chapter7习题答案
米什金 货币金融学 英文版习题答案chapter 7英文习题
Economics of Money, Banking, and Financial Markets, 11e, Global Edition (Mishkin) Chapter 7 The Stock Market, the Theory of Rational Expectations, and the Efficient Market Hypothesis7.1 Computing the Price of Common Stock1) A stockholder's ownership of a company's stock gives her the right toA) vote and be the primary claimant of all cash flows.B) vote and be the residual claimant of all cash flows.C) manage and assume responsibility for all liabilities.D) vote and assume responsibility for all liabilities.Answer: BAACSB: Analytical Thinking2) Stockholders are residual claimants, meaning that theyA) have the first priority claim on all of a company's assets.B) are liable for all of a company's debts.C) will never share in a company's profits.D) receive the remaining cash flow after all other claims are paid.Answer: DAACSB: Analytical Thinking3) Periodic payments of net earnings to shareholders are known asA) capital gains.B) dividends.C) profits.D) interest.Answer: BAACSB: Analytical Thinking4) The value of any investment is found by computing theA) present value of all future sales.B) present value of all future liabilities.C) future value of all future expenses.D) present value of all future cash flows.Answer: DAACSB: Analytical Thinking5) In the one-period valuation model, the value of a share of stock today depends uponA) the present value of both the dividends and the expected sales price.B) only the present value of the future dividends.C) the actual value of the dividends and expected sales price received in one year.D) the future value of dividends and the actual sales price.Answer: AAACSB: Analytical Thinking6) In the one-period valuation model, the current stock price increases ifA) the expected sales price increases.B) the expected sales price falls.C) the required return increases.D) dividends are cut.Answer: AAACSB: Reflective Thinking7) In the one-period valuation model, an increase in the required return on investments in equityA) increases the expected sales price of a stock.B) increases the current price of a stock.C) reduces the expected sales price of a stock.D) reduces the current price of a stock.Answer: DAACSB: Reflective Thinking8) In a one-period valuation model, a decrease in the required return on investments in equity causes a(n) ________ in the ________ price of a stock.A) increase; currentB) increase; expected salesC) decrease; currentD) decrease; expected salesAnswer: AAACSB: Reflective Thinking9) Using the one-period valuation model, assuming a year-end dividend of $0.11, an expected sales price of $110, and a required rate of return of 10%, the current price of the stock would beA) $110.11.B) $121.12.C) $100.10.D) $100.11Answer: CAACSB: Analytical Thinking10) Using the one-period valuation model, assuming a year-end dividend of $1.00, an expected sales price of $100, and a required rate of return of 5%, the current price of the stock would beA) $110.00.B) $101.00.C) $100.00.D) $96.19.Answer: DAACSB: Analytical Thinking11) In the generalized dividend model, if the expected sales price is in the distant futureA) it does not affect the current stock price.B) it is more important than dividends in determining the current stock price.C) it is equally important with dividends in determining the current stock price.D) it is less important than dividends but still affects the current stock price.Answer: AAACSB: Analytical Thinking12) In the generalized dividend model, a future sales price far in the future does not affect the current stock price becauseA) the present value cannot be computed.B) the present value is almost zero.C) the sales price does not affect the current price.D) the stock may never be sold.Answer: BAACSB: Analytical Thinking13) In the generalized dividend model, the current stock price is the sum ofA) the actual value of the future dividend stream.B) the present value of the future dividend stream.C) the present value of the future dividend stream plus the actual future sales price.D) the present value of the future sales price.Answer: BAACSB: Analytical Thinking14) Using the Gordon growth model, a stock's current price will increase ifA) the dividend growth rate increases.B) the growth rate of dividends falls.C) the required rate of return on equity rises.D) the expected sales price rises.Answer: AAACSB: Reflective Thinking15) Using the Gordon growth model, a stock's current price decreases whenA) the dividend growth rate increases.B) the required return on equity decreases.C) the expected dividend payment increases.D) the growth rate of dividends decreases.Answer: DAACSB: Reflective Thinking16) In the Gordon growth model, a decrease in the required rate of return on equityA) increases the current stock price.B) increases the future stock price.C) reduces the future stock price.D) reduces the current stock price.Answer: AAACSB: Reflective Thinking17) Using the Gordon growth formula, if D1 is $2.00, k e is 12% or 0.12, and g is 10% or 0.10, then the current stock price isA) $20.B) $50.C) $100.D) $150.Answer: CAACSB: Analytical Thinking18) Using the Gordon growth formula, if D1 is $1.00, k e is 10% or 0.10, and g is 5% or 0.05, then the current stock price isA) $10.B) $20.C) $30.D) $40.Answer: BAACSB: Analytical Thinking19) Using the Gordon growth model, if D1 is $.50, k e is 7%, and g is 5%, then the present value of the stock isA) $2.50.B) $25.C) $50.D) $46.73.Answer: BAACSB: Analytical Thinking20) One of the assumptions of the Gordon Growth Model is that dividends will continue growing at ________ rate.A) an increasingB) a fastC) a constantD) an escalatingAnswer: CAACSB: Analytical Thinking21) In the Gordon Growth Model, the growth rate is assumed to be ________ the required return on equity.A) greater thanB) equal toC) less thanD) proportional toAnswer: CAACSB: Analytical Thinking22) You believe that a corporation's dividends will grow 5% on average into the foreseeable future. If the company's last dividend payment was $5 what should be the current price of the stock assuming a 12% required return?Answer: Use the Gordon Growth Model.$5(1 + .05)/(.12 - .05) = $75AACSB: Analytical Thinking23) What rights does ownership interest give stockholders?Answer: Stockholders have the right to vote on issues brought before the stockholders, be the residual claimant, that is, receive a portion of any net earnings of the corporation, and the right to sell the stock.AACSB: Reflective Thinking7.2 How the Market Sets Stock Prices1) In asset markets, an asset's price isA) set equal to the highest price a seller will accept.B) set equal to the highest price a buyer is willing to pay.C) set equal to the lowest price a seller is willing to accept.D) set by the buyer willing to pay the highest price.Answer: DAACSB: Reflective Thinking2) Information plays an important role in asset pricing because it allows the buyer to more accurately judgeA) liquidity.B) risk.C) capital.D) policy.Answer: BAACSB: Analytical Thinking3) New information that might lead to a decrease in a stock's price might beA) an expected decrease in the level of future dividends.B) a decrease in the required rate of return.C) an expected increase in the dividend growth rate.D) an expected increase in the future sales price.Answer: AAACSB: Reflective Thinking4) A change in perceived risk of a stock changesA) the expected dividend growth rate.B) the expected sales price.C) the required rate of return.D) the current dividend.Answer: CAACSB: Reflective Thinking5) A stock's price will fall if there isA) a decrease in perceived risk.B) an increase in the required rate of return.C) an increase in the future sales price.D) current dividends are high.Answer: BAACSB: Reflective Thinking6) A monetary expansion ________ stock prices due to a decrease in the ________ and an increase in the ________, everything else held constant.A) reduces; future sales price; expected rate of returnB) reduces; current dividend; expected rate of returnC) increases; required rate of return; future sales priceD) increases; required rate of return; dividend growth rateAnswer: DAACSB: Reflective Thinking7) The global financial crisis lead to a decline in stock prices becauseA) of a lowered expected dividend growth rate.B) of a lowered required return on investment in equity.C) higher expected future stock prices.D) higher current dividends.Answer: AAACSB: Reflective Thinking8) Increased uncertainty resulting from the global financial crisis ________ the required return on investment in equity.A) raisedB) loweredC) had no impact onD) decreasedAnswer: AAACSB: Reflective Thinking7.3 The Theory of Rational Expectations1) Economists have focused more attention on the formation of expectations in recent years. This increase in interest can probably best be explained by the recognition thatA) expectations influence the behavior of participants in the economy and thus have a major impact on economic activity.B) expectations influence only a few individuals, have little impact on the overall economy, but can have important effects on a few markets.C) expectations influence many individuals, have little impact on the overall economy, but can have distributional effects.D) models that ignore expectations have little predictive power, even in the short run. Answer: AAACSB: Reflective Thinking2) The view that expectations change relatively slowly over time in response to new information is known in economics asA) rational expectations.B) irrational expectations.C) slow-response expectations.D) adaptive expectations.Answer: DAACSB: Analytical Thinking3) If expectations of the future inflation rate are formed solely on the basis of a weighted average of past inflation rates, then economists would say that expectation formation isA) irrational.B) rational.C) adaptive.D) reasonable.Answer: CAACSB: Analytical Thinking4) If expectations are formed adaptively, then peopleA) use more information than just past data on a single variable to form their expectations of that variable.B) often change their expectations quickly when faced with new information.C) use only the information from past data on a single variable to form their expectations of that variable.D) never change their expectations once they have been made.Answer: CAACSB: Reflective Thinking5) If during the past decade the average rate of monetary growth has been 5% and the average inflation rate has been 5%, everything else held constant, when the Federal Reserve announces that the new rate of monetary growth will be 10%, the adaptive expectation forecast of the inflation rate isA) 5%.B) between 5 and 10%.C) 10%.D) more than 10%.Answer: AAACSB: Reflective Thinking6) The major criticism of the view that expectations are formed adaptively is thatA) this view ignores that people use more information than just past data to form their expectations.B) it is easier to model adaptive expectations than it is to model rational expectations.C) adaptive expectations models have no predictive power.D) people are irrational and therefore never learn from past mistakes.Answer: AAACSB: Reflective Thinking7) In rational expectations theory, the term "optimal forecast" is essentially synonymous withA) correct forecast.B) the correct guess.C) the actual outcome.D) the best guess.Answer: DAACSB: Analytical Thinking8) If a forecast is made using all available information, then economists say that the expectation formation isA) rational.B) irrational.C) adaptive.D) reasonable.Answer: AAACSB: Analytical Thinking9) If a forecast made using all available information is NOT perfectly accurate, then it isA) still a rational expectation.B) not a rational expectation.C) an adaptive expectation.D) a second-best expectation.Answer: AAACSB: Analytical Thinking10) If expectations are formed rationally, then individualsA) will have a forecast that is 100% accurate all of the time.B) change their forecast when faced with new information.C) use only the information from past data on a single variable to form their forecast.D) have forecast errors that are persistently low.Answer: BAACSB: Analytical Thinking11) If additional information is not used when forming an optimal forecast because it is not available at that time, then expectations areA) obviously formed irrationally.B) still considered to be formed rationally.C) formed adaptively.D) formed equivalently.Answer: BAACSB: Analytical Thinking12) An expectation may fail to be rational ifA) relevant information was not available at the time the forecast is made.B) relevant information is available but ignored at the time the forecast is made.C) information changes after the forecast is made.D) information was available to insiders only.Answer: BAACSB: Analytical Thinking13) According to rational expectations theory, forecast errors of expectationsA) are more likely to be negative than positive.B) are more likely to be positive than negative.C) tend to be persistently high or low.D) are unpredictable.Answer: DAACSB: Analytical Thinking。
科特勒市场营销习题与答案
Chapter 7 Customer-Driven Marketing Strategy: Creating Value for Target Customers 1) When a company identifies the parts of the market it can serve best and most profitably, it is practicing ________.A) concentrated marketingB) mass marketingC) market targetingD) segmentingE) differentiationAnswer: CDiff: 2 Page Ref: 191Skill: ConceptObjective: 7-12) What are the four steps, in order, to designing a customer-driven marketing strategy?A) market segmentation, differentiation, positioning, and targetingB) positioning, market segmentation, mass marketing, and targetingC) market segmentation, targeting, differentiation, and positioningD) market alignment, market segmentation, differentiation, and market positioningE) market recognition, market preference, market targeting, and market insistenceAnswer: CDiff: 2 Page Ref: 191Skill: ConceptObjective: 7-13) Which type of segmentation centers on the use of the word when, such as when consumers get the idea to buy, when they actually make their purchase, or when they use the purchased item?A) behavioralB) psychographicC) occasionD) impulseE) emergencyAnswer: CDiff: 2 Page Ref: 196Skill: ConceptObjective: 7-24) Markets can be segmented into groups of nonusers, ex-users, potential users, first-time users, and regular users of a product. This method of segmentation is called ________.A) user statusB) usage ratesC) benefitD) behaviorE) loyalty statusAnswer: ADiff: 1 Page Ref: 197Objective: 7-25) Consumers can show their allegiance to brands, stores, or companies. Marketers can use this information to segment consumers by ________.A) user statusB) loyalty statusC) store typeD) brand preferenceE) usage rateAnswer: BDiff: 1 Page Ref: 197Skill: ConceptObjective: 7-26) Consumer and business marketers use many of the same variables to segment markets. Business marketers use all of the following EXCEPT ________.A) operating characteristicsB) purchasing approachesC) situational factorsD) personal characteristicsE) brand personalitiesAnswer: EDiff: 3 Page Ref: 198Skill: ConceptObjective: 7-27) When the size, purchasing power, and profiles of a market segment can be determined, it possesses the requirement of being ________.A) measurableB) accessibleC) substantialD) actionableE) observableAnswer: ADiff: 2 Page Ref: 200Skill: ConceptObjective: 7-28) When a business market segment is large or profitable enough to serve, it is termed ________.A) measurableB) accessibleC) substantialD) actionableE) differentiableAnswer: CDiff: 2 Page Ref: 200Objective: 7-29) To evaluate the different market segments your company serves, you would look at all of these factors EXCEPT which one?A) segment sizeB) segment growthC) segment structural attractivenessD) company valuesE) company resourcesAnswer: DDiff: 3 Page Ref: 201Skill: ConceptObjective: 7-310) Which of the following is NOT one of the reasons a segment would be less attractive to a company?A) strong competitorsB) substitute productsC) concentrated marketD) power of buyersE) power of suppliersAnswer: CDiff: 2 Page Ref: 201Skill: ConceptObjective: 7-311) The 55-year-old baby boomers share common needs in music and performers. When a music company decides to serve this group, the group is called a(n) ________.A) market segmentB) target marketC) well-defined marketD) differentiated marketE) undifferentiated marketAnswer: BDiff: 1 Page Ref: 201Skill: ConceptObjective: 7-312) When New Port Shipping uses segmented marketing, it targets several segments and designs separate offers for each one. This approach is called ________ marketing.A) undifferentiatedB) differentiatedC) targetD) individualE) nicheAnswer: BDiff: 2 Page Ref: 202Skill: ConceptObjective: 7-313) Developing a strong position within several segments creates more total sales than ________ marketing across all segments.A) undifferentiatedB) differentiatedC) nicheD) targetE) individualAnswer: ADiff: 3 Page Ref: 202Skill: ConceptObjective: 7-314) Using concentrated marketing, the marketer goes after a ________ share of ________.A) small。
信号与系统奥本海姆英文版课后答案chapter7
137Chapter 7 Answers7.1 From the Nyquist sampling theorem , we know that only if X (j w)=0 for |w| > w s /2 will be signal be recoverable from its samples. Therefore, X(jw)>5000л.7.2 From the Nyquist theorem ,we know that the sampling frequency in this case must be at least w s =2000п.In other words ,the sampling period should be at most T=2п/ (w s )=1＊10-3.Clearly ,only (a) and (e) satisfy this condition.7.3 (a) We can easily show that X(j w)=0 for |w| >4000п.Therefore, the Nyquist rate for this signal is w N =2(4000п)=8000п.(b)From the Tables 4.1 and 4.2 we know that X(j w) is a rectangular pulse for which X(j w)=0 for |w| > 4000п.Therefore, the Nyquist rate for this signal is w N =2(4000п)=800п.(c) From the Tables 4.1 and 4.2 we know that X(j w) is the convolution of two rectangular pulses each of which is zero for |w| > 4000п.Therefore ,X(j w)=0 for |w| >8000пand the Nyquist rate for this signal is w N =2(8000п)=16000п.7.4 If the signal x(t) has a Nyquist rate of w o ,then its Fourier transform X (j w)=0 for |w| > w o /2. (a) From chapter 4,y(t) = x (t) + x (t-1) −→←FTY (jw) = X (jw) + e -jwt X (jw).Clearly, we can only guarantee that Y (jw) =0 for |w| > w o /2. Therefore, the Nyquist rate for y(t) is also w o . (b) From chapter 4,y(t) = dtt dx )( −→←FTY (jw)= jw X(jw).Clearly, we can only guarantee that Y (jw) =0 for |w| > w o /2. Therefore, the Nyquist rate for y(t) is also w o . (c) From chapter 4,y(t) =x 2(t) −→←FTY (jw)= (1/2п)[X(jw)*X(jw)]Clearly, we can only guarantee that Y (jw) =0 for |w| > w o . Therefore, the Nyquist rate for y(t) is also 2w o . (d) From chapter 4,y(t)=x(t)cos (w o t) −→←FTY (jw)= (1/2)X(j(w- w o )) +(1/2)X(j(w+ w o )).Clearly, we can guarantee that Y (jw) =0 for |w| > w o + w o /2. Therefore, the Nyquist rate for y(t) is 3w o. 7.5 Using Table 4.2,p(t) −→←FT Tπ2∑∞-∞=-K T K )/2(πωδFrom Table 4.1 p(t-1) −→←FT Tπ2 e -jw T jk k eTk ππωδ2)2(-∞-∞=∑-. Since y(t)=x(t)p(t-1),we haveY (jw)= (1/2п)[X(jw)*FT{P(t-1)}]=(1/T)T jk K e Tk j X ππω2))2((-∞-∞=∑-Therefore, Y(j ω) consists of replicates of X(j ω) shifted by k2π/T and added to earth other (see Figure⎩⎨⎧≤=otherwiseT j H c ,0||,)(ωωωWhere (2/0ω)<c ω<(2π/T) - (2/0ω).7.6 Consider the signal w(t)=x 1(t)x 2(t).The Fourier transform W(j ω) of w(t) is given by W(j ω)=π21[])(*)(21ωωj X j X .Since 0)(1=ωj X for |ω|≥1ωand X 2(j ω)=0 for |ω|≥2ω, we may conclude that W(j ω)=0 for |ω|≥1ω+2ω.Consequently ，the Nyquist rate for w(t) iss ω=2(1ω+2ω).Therefore ,the maximum sampling138period which would still allow w(t) to be recovered is T=2π/(s ω)=π/(1ω+2ω). 7.7 We note thatx 1(t) =h 1(t)*{∑∞-∞=-n nT t nT x )()(δ}Form Figure 7.7 in the book ,we know that the output of the zero-order hold may be written as x 0(t)=h 0(t)* {∑∞-∞=-n nT t nT x )()(δ}where h 0(t) is as shown in Figure S7.7 By taking the Fourier transform of the two above equations, we have X 1(j ω)=H 1( j ω)X p ( j ω)X 0(j ω)=H 0( j ω) X p ( j ω)We now need to determine a frequency response H d ( j ω) for a filter which produces x 1(t) at its output when x 0(t) is its input. Therefore, we needX 0(j ω) H d ( j ω)= X 1(j ω)The triangular function h 1(t) may be obtained by convolving two rectangular pulses as shown in Figure S7.7Therefore,h 1(t)={(1/T ) h 0(t+T/2)}*{( 1/T ) h 0(t+T/2)} Taking the Fourier transform of both sides of the above equation, H 1( j ω)=T1e T j ω H 0( j ω) H 0( j ω) ThereforeX 1(j ω)= H 1( j ω) X p ( j ω)=T 1e T j ω H 0( j ω) H 0( j ω) X p ( j ω) =T1e Tj ω H 0( j ω) X 0(j ω)ThereforeH d ( j ω)=T1eTj ω H 0( j ω)=e2/jwT TT ωω)2/sin(2 7.8 (a) Yes, aliasing does occur in this case .This may be easily shown by considering the sinusoidal term of x(t) for k=5. This term is a signal of the form y(t)=(1/2)5sin(5πt).If x(t) is sampled as T=0.2, then we will always be sampling y(t) at exactly its zero-crossings (This is similar to the idea presented in Figure 7.17 of your textbook). Therefore ,the signal y(t) appears to be identical to the signal (1/2)5sin(0πt) for frequency 5π is a liased into a sinusoid of frequency 0 in the sampled signal.(b) The lowpass filter performs band limited interpolation on the signal ∧x(t).But since aliasing has alreadyresulted in the loss of the sinusoid (1/2)5sin(5πt),the output will be of the formx γ(t)=k k )21(40∑= sin(k πt)The Fourier series representation of this signal is of the form139x γ(t)=∑-=44k k a e )/(t k j π-Where a k =-j(1/2)1+kj(1/2)1+-k7.9 The Fourier transform X(jWe know from the results on impulse-train sampling thatG(jw)=∑∞∞--ωωk j X T ((1s )),Where T=2π/s ω=1/75.therefore,G(jw) is as shown in Figure S7.9 .Clearly, G(jw)=(1/T)X(j ω)=75 X(j ω) for |ω|≤50π.7.10 (a) We know that x(t) is not a band-limited signal. Therefore, it cannot undergo impulse-train sampling without aliasing.(b) Form the given X(j ω) it is clear that the signal x(t) which is bandlimited. That is, X(j ω)=0 for |ω|>0ω.Therefore, it must be possible to perform impulse-train sampling on this signal without experiencing aliasing. The minimum sampling rate required would bes ω=20ω,This implies that thesampling period can at most be T=2π/s ω=π/0ω(c) When x(t) undergoes impulse train sampling with T=2π/0ω,we would obtain the signal g(t) with Fourier transformG(jw)= T1∑∞-∞=-k T k j X ))/2((πωFigure S7.10It is clear from the figure that no aliasing occurs, and that X(jw) can be recovered by using a filter with frequency response T 0≤ωω≤0 H(jw)= 0 otherwiseTherefore, the given statement is true. 7.11 We know from Section 7.4 thatX d (ωj e )= T1∑∞-∞=-k cT k j X ))/2((πω(a) Since X d (ωj e) is just formed by shifting and summing replicas of X(jw),we may argue that ifX d (ωj e ) is real , then X(jw) must also be real(b) X d (ωj e) consists of replicas of X(jw) which are scaled by 1/T,Therefore,if X d (ωj e) has amaximum of 1, then X(jw) must also be real.(c) The region πωπ≤≤||4/3in the discrete-time domain corresponds to the regionT T /||)4/(3πωπ≤≤ in the discrete-time domain. Therefore ,if X d (ωj e )=0 forπωπ≤≤||4/3,then X(jw)=0 for πωπ2000||1500≤≤,But since we already have X(jw)=0 for140πω2000||≥,we have X(jw)=0 for πω1500||≥(d) In this case, sinceπ in discrete-time frequency domain corresponds to 2000π in the continuous-time frequency domain, this condition translates to X(jw)=(j(ω-2000π))7.12 Form Section 7.4 ,we know that the discrete and continuous-time frequencies Ω and ω are related by Ω=ω.Therefore, in this case for Ω=43π,we find the corresponding value of ω toω=43πT1=3000π/4=7500π7.13 For this problem ,we use an approach similar to the one used in Example 7.2 .we assume thatx c (t)=tT t ππ)/sin(The overall output isy c (t)= x c (t-2T)= )2()]2)(/sin[(T t T t T --ππForm x c (t). We obtain the corresponding discrete-time signal x d [n] to be x d [n]= x c (nT)= T1][n δalso, we obtain from y c (t),the corresponding discrete-time signal y d [n] to be y d [n]= y c (nT) =)2()]2(sin[(--n T n ππWe note that the right-hand side of the above equation is always zero when n ≠2.When n=2 ,wemay evaluate the value of ratio using L ,Hospital ,s rule to be 1/T ,Thereforey d [n]= T1]2[-n δWe conclude that the impulse response of the filter is h d [n]= ]2[-n δ7.14 For this problem ,we use an approach similar to the one used in Example 7.2.We assume that x c (t)= tT t ππ)]/sin[(The overall output isy c (t)=)2(T t x dt d c -=)2/()]2/()/[()/(T t T t T COS T ---πππ-2))2/(()]2/)(/sin[(T t T t T --πππForm x c (t) , we obtain the corresponding discrete-time signal x d [n] to be x d [n]= x c (nT)= T1][n δAlso, we obtain from yc(t),the corresponding discrete-time signal y d [n] to beY d [n]=y c (nT)=)2/1()]2/1(cos[)/(--n T n T πππ- )2/1()]2/1(sin[--n T n ππThe first term in rig πht-hang side of the above equation is always zero because cos[π(n-1/2)]=0, therefore, y d [n]= )2/1()]2/1(sin[--n T n ππWe conclude that the impulse response of the filter is h d [n]= )2/1()]2/1(sin[--n T n ππ7.15. in this problem we are interested in the lowest rate which x[n] may be sampled without the possibility of aliasing, we use the approach used in Example 7.4 to solve this problem. To find the lowest rate at which x[n] may be sampled while avoiding the possibility of aliasing, we must find an N such that (22≥Nπ)73πN ≤7/37.16 Although the signal x 1[n]=2sin(πn/2)/( πn) satisfies the first tow conditions, it does not satisfy the thirdcondition . This is because the Flurries transform X 1(e j ω) of this signal is rectangular pulse which is zero for π/2<|ω|<π/2 We also note that the signal x[n]=4[sin(πn/2)/(πn)]2 satisfies the first tow conditions. Fromour numerous encounters with this signal, we know that its Fourier transform X(e j ω) is given by the periodic141convolution of X 1(e j ω) with itself. Therefore, X(e j ω) will be a triangular function in the range 0≤|ω|≤π. This obviously satisfies the third condition as well. T therefore, the desired signal is x[n]=4[sin(πn/2)/(πn)]2.7.17 In this problem .we wish to determine the effect of decimating the impulse response of the given filter by a factor of 2. As explained in Section 7.5.2 ,the process of decimation may be broken up into two steps. In the first step we perform impulse train sampling on h[n] to obtain H p [n]∑∞-∞=k h[2k]δ[n-2k]The decimated sequence is then obtained using h 1[n]=h[2n]=h p [2n]Using eq (7.37), we obtain the Fourier transform H p (e j ω) of h p [n] to beH 1(e j ω)=H p (e jω/2)In other words , H 1(e j ω) is H p (e j ω/2) expanded by a factor of 2. This is as shown in the figure above. Therefore, h 1[n]=h[2n] is the impulse response of an ideal lowpass filter with a passband gain of unity and a cutoff frequency of π/27.18 From Figure 7.37,it is clear interpolation by a factor of 2 results in the frequency response getting compressed by a factor of 2. Interpolation also results in a magnitude sealing by a factor of 2. Therefore, in this problem, the interpolated impulse response will correspond to an ideal lowpass filter with cutoff frequency π/ and a passband gain of 2.7.19 The Fourier transform of x[n] is given by1 |ω|≤ω1X(e j ω)= 0 otherwiseThis is as shown in Figure 7.19.(a) when ω1 ≤3π/5, the Fourier transform X 1(e j ω) of the output of the zero-insertion system is shown inFigure 7.19. The output w(e j ω) of the lowpass filter is as shown in Figure 7.19. The Fourier transform of theoutput of the decimation system Y(e j ω) is an expanded or stretched out version of W(e j ω). This is as shown in Figure 7.19.therefore, y[n]=51nn πω)3/5sin(1(b) When ω1＞3π/5, the Fourier’s transform X 1(e j ω) of the output of the zero-insertion system is as shownin Figure 7.19 The output W(e j ω142The Fourier transform of the output of the decimation system Y(e j ω) bis an expanded or stretched outversion of W(e j ω) .This is as shown in Figure S7.19. Therefore,y[n]=][51n δ7.20 Suppose that X(e j ω) is as shown in Figure S7.20, then the Fourier transform X A (e j ω) of the output of theoutput of S A , the Fourier transform X 1(e j ω) of the output of the lowpass filter , and the Fourier transform X B (e j ω) of the output of S B are all shown in the figures below. Clearly this system accomplishes the filtering task .Figure S7.20(b) Suppose that X(e j ω) is as shown in Figure S7.20 ,then the Fourier transform X B (e j ω) of the output ofS B ,the Fourier transform X 1(e j ω)of the output of the first lowpass filter ,the Fourier transfore X A (e j ω) of theoutput of S A ,the Fourier transform X 2(e j ω) of the output of the first lowpass filter are all shown in the figure below .Clearly this system does not accomplish the filtering task. 7.21(a) The Nyquist rate for the given signal is 2×5000π=10000π. Therefore in order to be able to recover x(t)from x p (t) ,the sampling period must at most be T max =2π/10000π=2×10-4 sec .Since the sampling period used is T=10-4＜T max ,x(t) can be recovered from x p (t).(b) The Nyquist rate for the given signal is 2×15000π=30000π. Therefore in order to be able to recover x(t)from x p (t) ,the sampling period must at most be T max =2π/30000π=0.66×10-4 sec .Since the sampling period used is T=10-4＞T max , x(t) can not be recovered from x p (t).(c) Here,I m {X(j ω)} is not specified. Therefore, the Nyquist rate for the signal x(t) is indeterminate. Thisimplies that one cannot guarantee that x(t) would be recoverable from x p (t).(d) Since x(t) is real,we may conclude that X(j ω)=0 for |ω|＞5000. Therefore the answer to this part isidentical to that of part (a)(e) Since x(t) is real, X(j ω)=0 for |ω|＞15000π. Therefore the answer to this part is identical to that of part(b)(f) If X(j ω)=0 for |ω|＞ω1,then X(j ω)*X(j ω)=0 for |ω|＞2ω1,Therefore in this part X(j ω)=0 for |ω|＞7500. The Nyquist rate for this signal is 2×7500π=15000π. Therefore in order to be able to recover x(t) from x p (t) ,the sampling period must at most be T max =2π/15000π=1.33×10-4 sec .Since the sampling period used is T=10-4＜T max , x(t) can be recovered from x p (t). (g)If |X(j ω)|=0 for ω＞5000π,then X(j ω)=0 for |ω|＞5000π. Therefore the answer to this part is identical to that of part (a).7.22 Using the properties of the Fourier transform, we obtain Y(j ω)=X 1(j ω)X 2(j ω).Therefore, Y(j ω)=0 for |ω|＞1000π.This implies that the Nyquist rate for y(t) is2×1000π=2000π.Therefore, the sampling period T can at most be 2π/(2000π)=10-3sec. Therefore we have to use T<10-3sec in order to be able to recover y(t) from y p (t). 7.23(a) We may express p(t) asP(t)=p 1(t)-p 1(t-△);Where p 1(t)=∑∞-∞=∆-k k t )2(δnow,143P 1(j ω)=∆π∑∞-∞=∆-k )/(πωδTherefore,P(j ω)= P 1(j ω)-e -j ω∆P 1(j )ωIs as shown in figure S7.23. Now,X p (j ω)=)](*)([21ωωπjP j XTherefore, X p (j ω) is as sketched below for △<π/(2ωM ),The corresponding Y(j ω) is also sketched in figure S7.23.(b) The system which can be used to recover x(t) from x p (t) is as shown in FigureS7.23. (c) The system which can be used to recover x(t) from x(t) is as shown in FigureS7.23.(d) We see from the figures sketched in part (a) that aliasing is avoided when ωM ≤π/△.therefore, △max =π/ωM.7.24 we may impress s(t) as s(t)=s(t)-1,where s(t) is as shown in Figure S7.24 we may easily show thats (j )ω= ∑∞-∞=-∆k T k kT k )/2()/2sin(4πωδπFrom this, we obtainS(j =-=)(2)()ωπδωωj S∑∞-∞=-∆k T k k T k )/2()/2sin(4πωδπ-2)(ωπδ Clearly, S(j ω) consists of impulses spaced every 2π/T.(a) If △=T/3, thenS(j =)ω∑∞-∞=-k T k kk )/2()3/2sin(4πωδπ-2)(ωπδNow, since w(t)=s(t)x(t),πω21)(=j W ∑∞-∞=--k X T k j X kk )(2))/2(()3/2sin(4ωππωπTherefore, W(j ω)consists of replicas of X(j ω) which are spaced 2π/T apart. Tn order to avoid aliasing,ωW should be less that π/T. Therefore, T max =2π/ωW. (b) If △=T/3, then(a)(b)()jw Figure S7.24x144S(j =)ω∑∞-∞=-k T k k k )/2()4/2sin(4πωδπ-2)(ωπδ we note that S(j ω)=0 for k=0,±2, ±4,…..This is as sketched in Figure S7.24.Therefore, the replicas of X(j ω)in W(j ω) are now spaced 4π/T apart. Tn order to avoid aliasing,ωW should be less that2π/T. Therefore, T max =2π/ωW. 7.25 Here, x T (kT) can be written asX T (kT)= ∑∞-∞=--k nT x n k n k )()()](sin[ππNote that when n ≠k,0)()](sin[=--n k n k ππAnd when n=k,1)()](sin[=--n k n k ππ Therefore,x τ(kT)=x(kT)7.26. We note thatp(j ω)=Tπ2δ(ω－k2π/T)Also, since x p (t)=x(t)p(t).X p (j ω)=12π{ x(j ω) * P(j ω)}=1Tx(j(ω－k2π/T))Figure S7.26Note that as T increase, Tπ2－ω2 approaches zero. Also, we note that there is aliasingWhen2ω1-ω2<Tπ2－ω2<ω2If 2ω1-ω2≥0(as given) then it is easy to see that aliasing does not occur when 0≤Tπ2－ω2≤2ω1－ω2For maximum T, we must choose the minimum allowable value for Tπ2－ω2 (which is zero).This implies that T max =2π/ω2. We plot x p (j ω) for this case in Figure S7.26. Therefore, A=T, ωb =2π/T, and ωa =ωb －ω11457.27.(a) Let x 1(j ω) denote the Fourier transform of the signal x 1(t) obtained by multiplyingx(t) with e -j ω0t Let x 2(j ω) be the Fourier transform of the signal x 2(t) obtained at the output of the lowpass filter. Then, x 1(j ω), x 2(j ω),and x p (j ω),are as shown in Figure S7.27(b) The Nyquist rate for the signal x 2(t) is 2×(ω2－ω1)/2=ω2－ω1.Therefore, thep 7.28. (a) The fundamental frequency of x(t) is 20π rad/sec.From Chapter 4 we know that the Fourier transform of x(t) is given byX(j ω)=2πk ∞=-∞∑a k δ(ω－20πk).This is as sketched below. The Fourier transform x c (j ω) of the signal x c (t) is also Sketched in Figure S7.28. Note thatP(j ω)=2510π⨯3(2/(510))k k δωπ∞-=-∞-⨯∑Andx p (j ω)=12π[ x c (j ω)* p(j ω)]Therefore, x p (j ω) is as shown in the Figure S7.28.Note that the impulses from adjacentReplicas of x c (j ω) add up at 200π.Now the Fourier transform x(e j Ω) of the sequence x[n] is given byx(e j Ω)= x p (j ω)|ω=ΩT. This is as shown in the Figure S7.28.Since the impulses in x(e j ω) are located at multiples of a 0.1π,the signal x[n] is146(b) The Fourier series coefficients of X[n] aT π2(12)k , k=0,±1,±2,….,±9 a k =4T π(12)10 , k=10 7.29. x p (j ω)=1T((2/))k x j k T ωπ∞=-∞-∑x(jwe ), Y(jwe ), Y p (j ω),and Y c (j ω) are as shown in Figure S7.29. 7.30. (a) Since x c (t)=δ(t),we have()c dy t dt+y c (t)= δ(t) Taking the Fourier transform we obtainj ωY(j ω)+ Y(j ω)=1 Therefore , Y c (j ω)=11j ω+, and y c (t) =e -t u(t). (b) Since y c (t) =e -tu(t) , y[n]= y c (nT)= e -nT u[n].Therefore, j ωH(e j ω)=()()j W e Y e ω=11/(1)T j e e ω---=1－e －T e －j ωTherefore,h[n]= δ[n]－e －T δ[n －1]7.31. In this problem for the sake of clarity we will use the variable Ωto denote discretefrequency. Taking the Fourier transform of both sides of the given difference equation we obtainH(j e Ω)=()()j j Y e X e ΩΩ=1112j e -Ω-Given that the sampling rate is greater than the Nyquist rate, we have147x(j eΩ)=1Tx c (j Ω/T), for －π≤Ω≤π Therefore,Y(j eΩ)=1(/)12c j x j T T e -ΩΩ-For －π≤Ω≤π.From this we getY(j ω)= Y(jw eT)= =1()12c j Tx j T e ωω--For －π/T ≤ω≤π/T. in this range, Y(j ω)= Y c (j ω).Therefore,H c (j ω)=()()c c Y j X j ωω=1/112j TT e ω--7.32. Let p[n]=[14]k n k δ∞=-∞--∑.Then from Chapter 5,p(jwe )= e -j ω24π(2/4)k k δωπ∞=-∞-∑=2π2/4(2/4)j k k k eπδωπ∞--=-∞∑Therefore, G(jw e )=()1()()2j j p e x e d πθωθπθπ--⎰=32/4(2/4)01()4j k j k k e x e πωπ--=∑jwjwFigure S7.32Clearly, in order to isolate just x(jwe ) we need to use an ideal lowpass filter with Cutoff frequency π/4 and passband gain of 4. Therefore, in the range |ω|<π, 4, |ω|<π/4H(e j ω)= 0, π/4≤|ω|≤π7.33. Let y[n]=x[n][3]k n k δ∞=-∞-∑.ThenY(e j ω)=3(2/3)1()3j k k x eωπ-=∑Note that sin(πn/3)/(πn/3) is the impulse response of an ideal lowpass filter with cutoff frequency π/3 and passband gain of 3.Therefore,we now require that y[n] when passed through this filter should yieldx[n].Therefore, the replicas of x(e j ω) contained in Y(e j ω) should not overlap with one another. This ispossible only if x(e j ω) =0 for π/3≤|ω|≤π.7.34. In order to make x(e j ω) occupy the entire region from －πto π,the signal x[n]148must be downsampled by a factor of 14/3.Since it is not possible to directly downsample by a noninteger factor, we first upsample the signal by a factor of 3. Therefore, after the upsampling we will need toreduce the sampling rate by 14/3× 3=14. Therefore, the overall system for performing the sampling rate conversion isy[n][]2nx ,n=0,±3,±6,… y[n]=p[14n] ω[n]= 0, otherwise Figure S7.34)(e xp)(ωj d e x 7.36. (a) Let us decnote the sampled signaled signal by x p (t). We have∑∞-∞=-=n pnT t nT x t x )()()(δSince the Nyquist rate for the signal x(t) is T /2π,we can reconstruct the signal from x p (t). From Section 7.2,we know that)(*)()(t h t x t x p = whereTt T t t h /)/sin()(ππ=Thereforedtt dh t x dtt dx p )(*)()(=Denoting dtt dh )( by g(t),we have∑∞-∞=-==n pnT t g nT x t g t x dtt dx )()()(*)()(Therefore,2)/sin()/cos()()(tT t T tT t dtt dh t g πππ-==(b) No.7.37. We may write p(t) asp(t)=p 1(t)+p 1(t-∆),where∑∞-∞=-=k W k t t p )/2()(1πδTherefore,)()1()(1ωωωj p e j p j ∆-+= where∑∞-∞=-=k kW w j p )()(1ωδω149Let us denote the product p(t)f(t) by g(t).Then,)()()()()()()(11t f t p t f t p t f t p t g ∆-+== This may be written as)()()(11∆-+=t bp t ap t g Therefore,)(()(1)ωωωj p be a j G j ∆-+= with )(1ωj p is specified in eq.(s7.37-1). Therefore [])()(kw be a w j G k w jk -+=∑∞-∞=∆-ωδωWe now have)()()()(1t f t p t x t y = Therefore,[])(*)(21)(1ωωπωj x j G j Y =This give us[]))((2)(1kW j x be a Wj Y wjk -+=∑∆-ωπωIn the range 0<ω<W, we may specify Y 1(j ω) as[]))(()()()(2)(1W j x be a j x b a w j Y w jk -+++=∆-ωωπωsince )()()(112ωωωj H j Y j Y =, in the range 0<ω<W we may specify Y 2(j ω) as []))(()()()(2)(2W j x be a j x b a jW j Y W j -+++=∆-ωωπωSince ),()()(3t p t x t y =in the range 0<ω<W we may specify Y 3(j ω) as []))(()1()(22)(3W j x e j x W j Y W j -++=∆-ωωπωGive that 0<W △<π,we require that )()()(32ωωωj kx j Y j Y =+ for 0<ω<W. That is[][])())(()1(2)()(2ωωπωπj kx W j x e W j x jb ja a Ww j =-++++∆-This implies that01=+++∆-∆-W j Wj jbe ja e Solving this we obtainA=1, b= -1, When W △=π/2. More generally, we also geta=sin(W △)+)tan())cos(1(∆∆+W W and )sin()cos(1∆∆+-=W W bexcept when 2/π=∆W Finally, we also get [])2/(12jb ja Wk ++=π。
《商务英语函电》 Chapter 7
II. Fill in the blanks with the proper forms of the following words or
expressions.
1. captioned
2. With regaห้องสมุดไป่ตู้d to, so far
3. enabling
4. see that, avoid
5. the fact that
6. stress v./n. 着重强调；重点
1) stress + that clause
2) stress + n.
The sellers stressed the importance of establishing L/C in strict accordance with the stipulations of the contract.
6. relevant
7. in exact accordance with
8. drawing near
9. call, attention
III. Identify and correct the mistakes in the following sentences.
1. A. have
2. C. be opened
谨启
(B) 通知开证 敬启者：
我方第5781号订单订购的500匹柞丝绸，约在30日前 开出不可撤消的信用证，到期日为五三月十五日，特函提 请注意。
由于销售季节很快临近，我方客户急需此货，请尽快 交货，以便在季节开始时赶上旺销。
我们愿强调如延迟交货，无疑地会给我们造成不小的 困难。
对你方合作，预致谢意。
3. A. With regard to
当代医学英语答案chapter7复旦
当代医学英语答案chapter7复旦1、His remarks _____me that I had made the right decision. [单选题] *A.ensuredB.insuredC.assured(正确答案)D.assumed2、—Where ______ you ______ for your last winter holiday?—Paris. We had a great time. （）[单选题] *A. did; go(正确答案)B. do; goC. are; goingD. can; go3、Though my best friend Jack doesn’t get（）education, he is knowledgeable. [单选题] *A. ManyB. littleC. fewD. much(正确答案)4、Mr. White likes to live in a _______ place. [单选题] *A. quiteB. quiet(正确答案)C. quickD. quietly5、—______ my surprise, Zhu Hui won the first prize in the speech contest. —But I think he could, because he kept practicing speaking.（）[单选题] *A. To(正确答案)B. AboutC. ForD. In6、Could you tell me _____ to fly from Chicago to New York? [单选题] *A.it costs how muchB. how much does it costC. how much costs itD.how much it costs(正确答案)7、The manager demanded that all employees _____ on time. [单选题] *A. be(正确答案)B. areC. to beD. would be8、He always did well at school _____ having to do part-time jobs every now and then. [单选题] *A despite ofB. in spite of(正确答案)C. regardless ofD in case of9、In crowded places like airports and railway stations, you___ take care of your luggage. [单选题] *A. canB. mayC. must(正确答案)D. will10、66．—How much meat do you want?—________．[单选题] *A．Sorry, there isn't anyB．I can't give you anyC．Half a kilo, please(正确答案)D．Twelve yuan a kilo11、He held his（）when the results were read out. [单选题] *A. breath(正确答案)B. voiceC. soundD. thought12、Becky is having a great time ______ her aunt in Shanghai. （）[单选题] *A. to visitB. visitedC. visitsD. visiting(正确答案)13、Don't tell me the answer, I'll work out the problem _____. [单选题] *A .by meB. myself(正确答案)C. meD. mine14、No writer will be considered（）of the name until he writes a work. [单选题] *A. worthlessB. worthy(正确答案)C. worthwhileD. worth15、Everyone here is _______ to me. [单选题] *A. happyB. wellC. kind(正确答案)D. glad16、I gave John a present but he gave me nothing_____. [单选题] *A.in advanceB.in vainC.in return(正确答案)D.in turn17、( ) What other books have you read___ this English novel? [单选题] *A. besides(正确答案)B. exceptC.inD. about18、_____ the project, we'll have to work two more weeks. [单选题] *A. CompletingB. CompleteC. Having completedD.To complete(正确答案)19、_______ your parents at home last week? [单选题] *A. IsB. WasC. AreD. Were(正确答案)20、He _______ maths. [单选题] *A. does well in(正确答案)B. good atC. is well inD. does well at21、Julia’s on holiday in Shanghai _______. [单选题] *A. in a momentB. after a momentC. at the moment(正确答案)D. at any moment22、( ) You had your birthday party the other day,_________ [单选题] *A. hadn't you?B. had you?C. did you?D. didn't you?(正确答案)23、6．Hi, boys and girls. How are you ________ your posters for the coming English Festival at school? [单选题] *A．getting onB．getting offC．getting with (正确答案)D．getting24、--Why are you late for school today?--I’m sorry. I didn’t catch the early bus and I had to _______ the next one. [单选题] *A. wait for(正确答案)B. ask forC. care forD. stand for25、This year our school is _____ than it was last year. [单选题] *A. much more beautiful(正确答案)B. much beautifulC. the most beautifulD. beautiful26、—Whose book is it? Is it yours?—No, ask John. Maybe it’s ______.（）[单选题] *A. hersB. his(正确答案)C. he’sD. her27、The Titanic is a nice film. I _______ it twice. [单选题] *A. sawB. seeC. have seen(正确答案)D. have saw28、There are about eight ______ students in my school.（）[单选题] *A. hundred(正确答案)B. hundredsC. hundred ofD. hundreds of29、Look at those black clouds! Take ______ umbrella or ______ raincoat with you. （）[单选题] *A. a; anB. an; a(正确答案)C. an; anD. a; a30、She serves as a secretary in a university. [单选题] *A. 为…服务B. 担任…职务(正确答案)C. 竞争…服务D. 申请…职务。
第七章一维波动方程的解题方法与习题答案
第七章一维波动方程的傅里叶解小结及习题答案第二篇数学物理方程——物理问题中的二阶线性偏微分方程及其解法Abstracts:1、根据物理问题导出数理方程—偏微分方程；2、给定数理方程的附加条件：初始条件、边界条件、物理条件(自然条件，连接条件)，从而与数理方程一起构成定解问题；3、方程齐次化；４、数理方程的线性导致解的叠加。
一、数理方程的来源和分类（状态描述、变化规律）1、来源I．质点力学：牛顿第二定律Fmr连续体力学弦2u(r,t)弹性体力学杆振动：22波动方程);au(r,t)0(2t(弹性定律)膜流体力学：质量守恒律：(v)0;t热力学物态方程：v1(v)vpf0(Eulereq.).tII.麦克斯韦方程DddD;EdlBdsEB;Bd0B0;Hdl(jD)dsHjD.Eu,BA,u,A满足波动方程。
Lorenz力公式力学方程；Maxwelleqs.+电导定律电报方程。
III.热力学统计物理热传导方程：扩散方程：Ttt2kT2D0;0.特别:稳态（0t）:20(Laplaceequation).IV.量子力学的薛定谔方程：2u2.iuVut2m2.分类物理过程方程数学分类振动与波波动方程2u 12u22at双曲线输运方程能量：热传导质量：扩散ut20ku抛物线1稳态方程Laplaceequation 2u0椭圆型二、数理方程的导出推导泛定方程的原则性步骤：（1）定变量：找出表征物理过程的物理量作为未知数（特征量），并确定影响未知函数的自变量。
（2）立假设：抓主要因素，舍弃次要因素，将问题“理想化”---“无理取闹”（物理趣乐）。
（3）取局部：从对象中找出微小的局部（微元），相对于此局部一切高阶无穷小均可忽略---线性化。
（4）找作用：根据已知物理规律或定律，找出局部和邻近部分的作用关系。
（5）列方程：根据物理规律在局部上的表现，联系局部作用列出微分方程。
Chapter7一维波动方程的傅里叶解第一节一维波动方程-弦振动方程的建立1.弦横振动方程的建立（一根张紧的柔软弦的微小振动问题）（1）定变量：取弦的平衡位置为x轴。
chap7中级宏观经济学答案 华中科技大学
Microeconomics, 4e (Perloff)Chapter 7 Costs7.1 Measuring Costs1) Economic costs of an input includeA) only implicit costs.B) only explicit costs.C) both implicit and explicit costs.D) whatever management wishes to report to the shareholders.Answer: CTopic: Measuring Costs2) The cost of waiting two months for health care to address a debilitating problem in Canada is most accurately described asA) an explicit cost.B) an accounting cost.C) no real cost.D) an opportunity cost.Answer: DTopic: Measuring Costs3) Sarah earns $40,000 per year working for a large corporation. She is thinking of quitting this job to work full time in her own business. She will invest her savings of $50,000 (which currently has an annual 10% rate of return) into the business. Her annual opportunity cost of this new business isA) $0.B) $40,000.C) $45,000.D) $90,000.Answer: CTopic: Measuring Costs4) The Nifty Gum Co. has purchased a large parcel of land for $1 million. The company recently discovered that the land is contaminated and is worthless to all possible buyers. The opportunity cost of the land isA) $0.B) $1 million.C) some amount greater than $0 but less than $1 million.D) equal to the cost of the factory that was planned to be built there.Answer: ATopic: Measuring Costs5) Johnny has worked as a CPA for five years and wants to open his own public accounting practice. The cost of his college degree in accounting representsA) the opportunity cost of this endeavor.B) a sunk cost.C) an expense.D) a variable cost.Answer: BTopic: Measuring Costs6) Economists proclaim that competitive firms make zero economic profit in the long run. This shows howA) detached economists are from the real world.B) unrealistic economic theory is.C) firms cover all their cost, both monetary and non-monetary.D) firms cover only monetary cost when economic profits are zero.Answer: CTopic: Measuring Costs7) If a firm buys a building so as to have office space for its workers, the monthly opportunity cost of the building is best measured asA) the monthly mortgage payment the firm must pay.B) the price the firm paid divided by twelve.C) zero.D) the rent the firm could earn if it rented the building to another firm.Answer: DTopic: Measuring CostsFor the following, please answer "True" or "False" and explain why.8) When buying a piece of equipment, it is always best for the firm to pay cash instead of borrowing the funds since this renders the equipment less costly.Answer: False. It depends. The opportunity cost of the capital when paying cash is the interest the firm receives on its cash reserves. This is an implicit cost. The opportunity cost of the capital when the funds are borrowed is the interest the firm must pay to the lender. This is an explicit cost. If the rate the firm receives on its cash reserves exceeds the rate at which it borrows, the firm is better off borrowing the funds to buy the equipment.Topic: Measuring Costs9) Four years after graduating from college you must decide if you want to go on as an accountant (your college major) or if you want to make a career change and become a singer. The cost of your education will matter for your decision.Answer: False. At this point the cost of your education represents a sunk cost and therefore should not figure into your decision. You incur it no matter what decision you make.Topic: Measuring Costs10) An accountant may amortize the expense of a durable good by dividing the total amount spent on the good by the number of years the good is expected to last. An economist may amortize the expense of a durable and never fully account for the total expense.Answer: True. The accountant uses a set of predetermined rules to amortize the total expense of the good. The economist amortizes based on the opportunity cost of the good, which may never sum to the total expense of the good.Topic: Measuring Costs11) Your company makes copper pipes. Over the years, you have collected a large inventory of raw copper. The production process involves melting the copper and shaping it into pipes. You also have a large stockpile of pennies. Suppose the price of copper rises so much that the copper in the penny becomes worth more than one cent. Should you melt down your pennies?Answer: This problem appeared as a puzzle in the Journal of Economic Perspectives (Winter, 1988). It is true (in this problem) that the pennies when melted currently have a value greater than one cent. Yet, the price of copper can fluctuate. If the price of copper stays high, it does not matter if you melt pennies or not. However, if the price of copper falls so that the value of the copper in the penny falls below one cent, your unmelted pennies are still worth one cent. Your melted pennies would be worth less than one cent. Thus, as long as you have some other source of copper, you are better off melting that copper and not the pennies.Topic: Measuring Costs12) You have two career options. You can work for someone else for $50,000 a year, or, you can run your own business, with an annual revenue of $100,000, and explicit costs of $40,000 annually. Explain which career option a profit-maximizer would select and why.Answer: In the absence of other implicit costs a profit-maximizer will run their own business. The business owner will receive $100,000 - $40,000 = $60,000. The opportunity cost is only $50,000.Topic: Measuring Costs7.2 Short-Run Costs1) A firm's marginal cost can always be thought of as the change in total cost ifA) the firm produces one more unit of output.B) the firm buys one more unit of capital.C) the firm's average cost increases by $1.D) the firm moves to the next highest isoquant.Answer: ATopic: Short-run Costs2) Fixed costs areA) a production expense that does not vary with output.B) a production expense that changes with the quantity of output produced.C) equal to total cost divided by the units of output produced.D) the amount by which a firm's cost changes if the firm produces one more unit of output.Answer: ATopic: Short-run Costs3) Variable costs areA) a production expense that does not vary with output.B) a production expense that changes with the quantity of output produced.C) equal to total cost divided by the units of output produced.D) the amount by which a firm's cost changes if the firm produces one more unit of output.Answer: BTopic: Short-run Costs4) Which of the following statements is NOT true?A) AC = AFC + AVCB) C = F + VCC) AVC = wage/MP LD) AFC = AC - AVCAnswer: CTopic: Short-run Costs5) Joey's Lawncutting Service rents office space from Joey's dad for $300 per month. Joey's dad is thinking of increasing the rent to $400 per month. As a result Joey's marginal cost of cutting grass willA) increase by $100 divided by the amount of grass cut.B) increase by $100.C) decrease by $100.D) not change.Answer: DTopic: Short-run Costs6) Suppose a firm can only vary the quantity of labor hired in the short run. An increase in the cost of capital willA) increase the firm's marginal cost.B) decrease the firm's marginal cost.C) have no effect on the firm's marginal cost.D) More information is needed to answer the question.Answer: CTopic: Short-run Costs7) Suppose the total cost of producing T-shirts can be represented as TC = 50 + 2q. The marginal cost of the 5th T-shirt isA) 2.B) 10.C) 12.D) 60.Answer: ATopic: Short-run Costs8) Suppose the total cost of producing T-shirts can be represented as TC = 50 + 2q. The average cost of the 5th T-shirt isA) 2.B) 12.C) 52.D) 60.Answer: BTopic: Short-run Costs9) Suppose the total cost of producing T-shirts can be represented as TC = 50 + 2q. Which of the following statements is TRUE at all levels of production?A) MC = AVCB) MC = ACC) MC > AFCD) All of the above.Answer: ATopic: Short-run Costs10) Suppose the short-run production function is q = 10 * L. If the wage rate is $10 per unit of labor, then AVC equalsA) q.B) q/10.C) 10/q.D) 1.Answer: DTopic: Short-run Costs11) Suppose the short-run production function is q = 10 * L. If the wage rate is $10 per unit of labor, then MC equalsA) q.B) q/10.C) 10/q.D) 1.Answer: DTopic: Short-run Costs12) If average cost is decreasingA) Marginal cost equals average cost.B) Marginal cost exceeds average cost.C) Marginal cost is less average cost.D) Not enough informationAnswer: CTopic: Short-run Costs13) If average cost is positiveA) Marginal cost equals average cost.B) Marginal cost exceeds average cost.C) Marginal cost is less average cost.D) Not enough informationAnswer: DTopic: Short-run Costs14) Suppose the short-run production function is q = L0.5. If the marginal cost of producing the tenth unit is $5, what is the wage per unit of labor?A) $1B) $0.5C) $0.25D) It cannot be determined without more information.Answer: CTopic: Short-run Costs15) Suppose the short-run production function is q = 10 * L. If the wage rate is $10 per unit of labor, then AFC equalsA) 0.B) 1.C) 10/q.D) It cannot be determined from the information provided.Answer: DTopic: Short-run Costs16) When a firm produces one unit, the variable cost is $3. When the firm produces two units, the variable cost is $6. What is the marginal cost associated with two units of production?A) $2B) $0.5C) $6D) $3Answer: DTopic: Short-run Costs17) In the short run, the point at which diminishing marginal returns to labor begin is the point at which the marginal cost curveA) peaks.B) bottoms out.C) is upward sloping.D) is downward sloping.Answer: BTopic: Short-run Costs18) If the marginal cost of producing a good is increasing as a firm produces more of the good, then which of the following must be TRUE?A) AFC is rising.B) AVC is rising.C) MC > AVC.D) MPL is falling.Answer: DTopic: Short-run Costs19) If the average cost of producing a good is increasing as a firm produces more of the good, then which of the following must be TRUE?A) AFC is falling.B) AVC is rising.C) MC > AVC.D) All of the above.Answer: DTopic: Short-run Costs20) If a particular production process is subject to diminishing marginal returns to labor at every level of output, then at every level of outputA) AC is upward sloping.B) MC exceeds AVC.C) AFC is constant.D) All of the above.Answer: BTopic: Short-run Costs21) Marginal Cost is equal toA) the increase in total cost from increasing the amount of labor by one unit.B) the increase in average cost from increasing the amount of labor by one unit.C) Both A and B.D) Neither A nor B.Answer: CTopic: Short-run Costs22) Suppose each worker must use only one shovel to dig a trench, and shovels are useless by themselves. In the short run, an increase in the price of shovels will result inA) fewer shovels being purchased.B) more workers being hired.C) a decrease in the firm's output.D) no change in the firm's output.Answer: DTopic: Short-run Costs23) Which of the following will cause the marginal cost curve of making cigarettes to shift?A) A $5 million penalty charged to each cigarette maker.B) A $1 per pack tax on cigarettes.C) A $1 million advertising campaign by the American Cancer Society.D) All of the above.Answer: BTopic: Short-run Costs24) Which of the following will cause the average cost curve of making cigarettes to shift?A) A $5 million penalty charged to each cigarette maker.B) A $1 per pack tax on cigarettes.C) A $1 an hour wage increase paid to all cigarette production workers.D) All of the above.Answer: DTopic: Short-run Costs25) Which of the following will cause the average fixed cost curve of making cigarettes to shift?A) A $5 million penalty charged to each cigarette maker.B) A $1 per pack tax on cigarettes.C) A $3 per hour wage increase.D) An increase in the demand for cigarettes.Answer: ATopic: Short-run Costs26) A specific tax of $1 per unit of output will affect a firm'sA) average total cost, average variable cost, average fixed cost, and marginal cost.B) average total cost, average variable cost, and average fixed cost.C) average total cost, average variable cost, and marginal cost.D) marginal cost only.Answer: CTopic: Short-run CostsFor the following, please answer "True" or "False" and explain why.27) The "Law of Diminishing Marginal Returns" could also be termed the "Law of Increasing Marginal Costs."Answer: True. Since MC = w/MP L in the short run, the fact that MPL eventually declines means that MC must eventually increase.Topic: Short-run Costs28) The marginal cost curve intersects the average fixed cost curve at its minimum.Answer: False. Marginal cost intersects average variable cost (and average cost) at its minimum.Topic: Short-run Costs29) A consumer purchases a book by driving across town to a bookstore, standing in line for five minutes to pay the cashier, and then pays $5. The same book is purchased by another consumer who spends 2 minutes placing the order over the internet for $10. The book necessarily cost the first consumer less.Answer: False. The opportunity cost of driving across town and standing in line may have raised the total cost of the book to the first consumer to more than $10.Topic: Short-run Costs30) A firm's production function for pretzels is shown in the above figure. If the firm's fixed cost equals $100 per time period and the wage rate equals $1 per unit of labor per time period, calculate the firm's MC, AVC, and AC schedules. Do these cost functions follow the general rules concerning the relationships between MC, AVC and AC?Answer:❑✌☞ ✌✞✌ MC > AVC, AVC is rising.MC < AC, AC is falling.Topic: Short-run Costs31) Explain why the marginal cost curve intersects a U-shaped average cost curve at its minimum point. Answer: At low quantities, the average cost curve declines as the quantity increases. The marginal cost is below the average cost. The marginal cost represents the cost of an additional unit of production. Thus, as the marginal cost curve declines, this pulls the average cost down from its previous level. Then, the marginal cost curve will begin to rise. However, the marginal cost is still below the average cost, which will continue to lower the average cost. When the two costs are equal the marginal cost will leave the average cost unchanged. Then, the marginal cost will be above the average cost so it will start to pull up the average cost. Thus, the marginal cost curve will intersect the average cost curve at its minimum point.Topic: Short-run Costs7.3 Long-Run Costs1) In the long run, fixed costs areA) sunk.B) avoidable.C) larger than in the short run.D) not included in production decisions.Answer: BTopic: Long-run Costs2) The slope of the isocost line tells the firm how muchA) capital must be reduced to keep total cost constant when hiring one more unit of labor.B) capital must be increased to keep total cost constant when hiring one more unit of labor.C) more expensive a unit of capital costs relative a unit of labor.D) the isocost curve will shift outward if the firm wishes to produce more.Answer: ATopic: Long-run Costs3) Which of the following does NOT represent a possible shape of the long-run average cost curve?A) downward-slopingB) upward-slopingC) U-shapedD) verticalAnswer: DTopic: Long-run Costs4) The slope of the isoquant tells the firm how muchA) output increases when labor increases by one unit.B) output increases when capital and labor are doubled.C) capital must decrease to keep output constant when labor increases by one unit.D) a unit of capital costs relative to the cost of labor.Answer: CTopic: Long-run Costs5) If an isocost line crosses the isoquant twice, a cost minimizing firm willA) use a different isocost line to select the bundle of inputs.B) use the input bundle associated with the intersection on the higher point of the isoquant.C) use the input bundle associated with the intersection on the lower point of the isoquant.D) Both B and C.Answer: ATopic: Long-run Costs6) When the isocost line is tangent to the isoquant, thenA) MRTS = w/r.B) the firm is producing that level of output at minimum cost.C) the last dollar spent on capital yields as much extra output as the last dollar spent on labor.D) All of the above.Answer: DTopic: Long-run Costs7) A firm can minimize cost byA) picking the bundle of inputs where the lowest isocost line touches the isoquant.B) picking the bundle of inputs where the isoquant is tangent to the isocost line.C) picking the bundle of inputs where the last dollar spent on one input gives as much extra output as the last dollar spent on any other input.D) All of the above.Answer: DTopic: Long-run Costs8) When the isocost line is tangent to the isoquant, thenA) MPL = MPK.B) the firm is producing that level of output at minimum cost.C) the firm has achieved the right economies of scale.D) All of the above.Answer: BTopic: Long-run Costs9) If the wage in increases the isocost line willA) stay the same.B) shift outward in parallel fashion.C) rotate inward around the point where only capital is employed in production.D) shift inward in parallel fashion.Answer: CTopic: Long-run Costs10) If the isoquants are straight lines or L-shaped, then a cost-minimizing firm willA) not be able to minimize costs.B) find the lowest isocost line touching the relevant isoquant.C) find the highest isocost line touching the relevant isoquant.D) choose not to produce any output.Answer: BTopic: Long-run Costs11) If the marginal rate of technical substitution for a cost minimizing firm is 10, and the wage rate for labor is $5, what is the rental rate for capital in dollars?A) .5B) 1C) 2D) 10Answer: ATopic: Long-run Costs12) Suppose MPL = 0.5 * (q/L) and MPK = 0.5 * (q/K). In the long run, the firm will hire equal amounts of capital and laborA) all of the time.B) only when w = r.C) only when w = 0.5 * r.D) at no point in time.Answer: BTopic: Long-run Costs13) Suppose that each worker must use only one shovel to dig a trench, and shovels are useless by themselves. In the long run, an increase in the price of shovels will result inA) fewer shovels being purchased to produce the same number of trenches.B) more workers being hired to produce the same number of trenches.C) the firm wishing to produce more trenches.D) no change in the firm's input mix.Answer: DTopic: Long-run Costs14) Suppose that each worker must use only one shovel to dig a trench, and shovels are useless by themselves. In the long run, the firm will experienceA) increasing returns to scale.B) constant returns to scale.C) decreasing returns to scale.D) The returns to scale cannot be determined from the information provided.Answer: BTopic: Long-run Costs15) Suppose that each worker must use only one shovel to dig a trench, and shovels are useless by themselves. In the long run, the firm's cost function isA) TC = (w/r) * q.B) TC = (w + r)/q.C) TC = (w + r).D) TC = (w + r) * q.Answer: DTopic: Long-run Costs16) At the XYZ Co., a unit of capital costs 3 times as much as a unit of labor. If the isoquants are convex, and the firm does not change its input mix in the long run, we can conclude thatA) MPK = 3 * MP L.B) the firm will not hire any capital.C) the firm will hire 3 times as much labor as capital.D) the firm will hire 3 times as much capital as labor.Answer: ATopic: Long-run Costs17) The production of cigarettes is highly automated; however, a worker is required to monitor each machine. Machines and workers do not interact with one another. Given this information, there are most likelyA) economies of scale.B) economies of scope.C) constant returns to scale.D) increasing returns to scale.Answer: CTopic: Long-run Costs18) Suppose that capital and labor must be kept in a fixed proportion to produce a particular good. For example, digging a trench requires one worker who has one shovel. What does this imply about returns to scale?A) There are constant returns to scale.B) There are increasing returns to scale.C) There are decreasing returns to scale.D) Nothing.Answer: ATopic: Long-run Costs19) A change in relative factor prices will always result inA) a change in the slope of the isoquants.B) a tangency between the new isocost line and a new isoquant.C) a rotation of the isocost lines.D) All of the above.Answer: CTopic: Long-run Costs20) Assuming that w and r are both positive, if the long-run expansion path is horizontal, thenA) MP K = 0.B) MRTS is a function of capital only.C) w = r.D) All of the above.Answer: BTopic: Long-run Costs21) The above figure shows the long-run expansion path. The long-run average cost curve will beA) horizontal.B) downward sloping.C) upward sloping.D) vertical.Answer: BTopic: Long-run Costs22) The long run average cost curve may initially slope downward due toA) decreasing average fixed costs.B) increasing marginal returns.C) economies of scale.D) All of the above.Answer: CTopic: Long-run Costs23) If a production function is represented as q = LαKβ, the long-run average cost curve will be horizontal as long asA) a + b = 0.B) a + b = 1.C) q > 0.D) L = K.Answer: BTopic: Long-run Costs24) If there are diseconomies of scale within a given range of output, which of following is(are) TRUE?A) The short-run average cost curve must be upward sloping within that range of output.B) The long-run average cost curve must be upward sloping within that range of output.C) Long-run average cost must equal short-run average cost.D) All of the above.Answer: BTopic: Long-run Costs25) The total cost of producing one unit is $50. The total cost of producing two units is $75. At a production level of two units, the cost function exhibitsA) economies of scale.B) rising average costs.C) increasing marginal costs.D) constant returns to scale.Answer: ATopic: Long-run CostsFor the following, please answer "True" or "False" and explain why.26) If increasing returns to scale are present, the long-run average cost increases as more output is produced. Answer: False. Increasing returns to scale imply that with a doubling of inputs, output more than doubles. Since average cost is the ratio of total cost divided by output, this increase in inputs will cause the numerator to be just double the old value while the new denominator is more than double the old value. As a result, long-run average cost falls as more output is produced.Topic: Long-run Costs27) Economies of scale and Increasing Returns to Scale are the same thing looked at from either the production or cost perspective.Answer: False. Increasing returns to scale imply economies of scale but the reverse is not true. A firm can experience economies of scale for other reasons (without increasing returns to scale)Topic: Long-run Costs28) Explain the difference between fixed costs in the short run and fixed costs in the long run.Answer: In the short run fixed costs are sunk; in the long run, fixed costs are avoidable.Topic: Long-run Costs29) What are the functions for MC and AC if TC = 100q + 100q2? Are the returns to scale increasing, decreasing, or constant?Answer: MC = 100 + 200qAC = 100 + 100qSince AC increases with an increase in output, there are decreasing returns to scale.Topic: Long-run Costs30) Explain how a firm can have constant returns to scale in production and economies of scale in cost. Answer: A firm can have constant returns to scale in production at every output level. If the firm doubled all inputs the output would double. However, the firm may have a decreasing average cost. As more inputs areused and output increases, the average cost declines, which is known as economies of scale.Topic: Long-run Costs31) Explain why the long-run total cost curve, not the short-run total cost curve, shows the lowest cost of producing any level of output. Is there an exception?Answer: In the long run, all costs are variable so the firm can select the least-cost mix of all inputs to produce any given quantity. The exception would be at minimum long-run cost where min. LR and min. SR costs are equal.Topic: Long-run Costs32) A local non-profit group prints a weekly newsletter. Professional typists earn $10 per hour and can type 2 pages per hour. Unpaid volunteers can type only 1 page per hour. Measuring hours of professional typist services on the vertical axis and hours of unpaid volunteer typist services on the horizontal axis, draw the relevant isoquant and isocost curves if the newsletter is 10 pages long. What input mix is chosen by the non-profit group if they wish to minimize the cost of the newsletter? If the group will reimburse volunteers for expenses (lunch, driving), how much must the reimbursement be for your answer to change? Answer:See the above figure. The isoquant is a straight line with a slope of 1/2. The group can use either 5 pros, 10 volunteers, or some combination of the two. The isocost curves are horizontal since volunteers are free. As a result, the lowest isocost curve is achieved by hiring all volunteers. If the group reimbursed volunteers for expenses (lunch, driving, etc.) then the group will still hire all volunteers as long as they do not cost more than $5 per hour.Topic: Long-run Costs33) A firm pays $5 for each unit of capital. Labor costs $5 per hour for the first 10 hours and $10 per hour for every hour thereafter. Draw the isocost curves for total costs of $50 and $100.Answer:See the above figure.Topic: Long-run Costs34) To dig a trench, each worker needs a shovel. Workers can use only one shovel at a time. Workers without shovels do nothing, and shovels cannot operate on their own. Graphically determine the number of shovels and workers used by a firm to dig 2 trenches when:(a) w = 10 and r = 10(b) w = 10 and r = 5Answer:See the above figure. Because the production process requires fixed proportions of K and L, the firm cannot change input mix when the relative factor costs change.Topic: Long-run Costs35) Suppose the production function is q = 12 L0.25K0.75. Determine the long-run capital-to-labor ratio (K/L) if the cost a unit of capital (r) is three times the cost of a unit of labor (w).Answer: The firm minimizes costs by setting MRTS = w/r. MRTS = MP L/MP K = K/3L = 1/3 = w/r. This firm will set K/L equal to one.Topic: Long-run Costs36) "If the wage rate paid to one form of labor is twice the cost of another form of labor, the first type of labor must be twice as productive." Comment.Answer: This is true. Firms minimize cost by setting the ratio of marginal productivity per unit cost equally across all inputs. If one form of labor is twice as expensive as another, the firm will want the MP of the first type of labor to be twice that of the second.Topic: Long-run Costs。
Chapter 7 A trip to the theatre答案(1)1
Chapter 7 A trip to the theatreI. Phrases 1. 让某人戴上面具 2. 强迫某人离开家 3. 在岛上安家 4. 爱上某人 5. 在深夜给某人唱歌 6. 同意与某人结婚 7. 在…中间 8. 把某人投进监狱 9. 拉下他的面具 10. 对…感到震惊 11. 在所有的观众前 12. 同情某人 13. 喜极而泣 14. 把某人带到安全地方 15. 闯进来；闯进公寓 16. 在那时 17. 与某人的关系 18. 远离、不介入 19. 改变主意 II. Sentence patterns1. be/ keep/ get in touch with 与 … 保持联系be out of touch with 和 ... 失去联系(和 ... 不接触)I kept in touch with my good friend by writing letters.= I contacted with my good friend by writing letters.2. v. 给……赠送 present sb. with sth. = present sth, to sb.Jan’s parents presented her with a piano.= Jan’s parents gave her a piano as a present.3. fall in love with …“爱上”强调动作be in love with …“爱着”强调状态4. pull on / off “穿上” “脱下” 强调瞬间动作；“有费力，用力拉”含义 。
Pull on the socks!put on /off “穿上” “脱下” 强调瞬间动作；很容易，不费劲Put on your raincoat! It is raining hard!5. act as…充当、担任 Mr. Lin works as an engineer. =Mr. Lin acts as an engineer.make someone wear a maskforce sb. to leave homemake one ’s home on the islandfall in love with someonesing to someone late at nightagree to marry someonein the middle ofput sb. in a prisonpull off his maskbe shocked at …in front of the whole audiencefeel sorry for someonecry with joytake someone to safetyburst in / into the flatat that momentone ’s relationship with sb.stay out ofchange one ’s mind6. so… that …. “如此…以致…”也可以跟“too…to…”转换。
Chapter 7 Nobody wins 11
Chapter 7 Nobody wins! P93-94 (中文) 111．以每秒30万公里的速度传播travel at a speed of 300,000 km per second2．愚弄某人/ 被某人愚弄play tricks on sb. / be tricked by sb.3．引起潮汐/ 获得自由cause the sea to move / get (be ) free4．在服刑中/ 成为一个囚犯be in prison / become a prisoner5．在他的袋鼠汤晚餐以后after his supper of kangaroo soup6．躺在床上/ 病倒在床上（过，过分）lie down on the bed / lie in bed (lay, lain, lying) 7．倒下熟睡/ 感到倦意fall asleep / feel sleepy8．很响地打鼾/ 震动了山洞snore loudly / shake the cave9．一支强大的激光枪/ 激光束 a powerful laser torch / laser beam10．在一个塑料盒里/ 塑料be in a plastic case / plastics11．吸走某物/ 袭击某人attract sth. / attack sb.12．用它来从笼子里逃走use it to escape from the cage13．熔化钢条/ 用你的大脑melt the steel bars / use your brains14．打断某人，插嘴/ 对某人低声说interrupt sb. / whisper to sb.15．太弱小而不能打开门be too weak to open the door16．躲藏在袋鼠中间（过，过分）hide among the kangaroos ( hid, hidden )17．片刻之后（三种）moments later, after a while, after a few moments 18．醒来/ 叫醒某人（过，过分）wake up / wake sb. up ( woke, woken ) 19．瞄准它的眼睛/ 指向它aim the torch at his eye / point at it20．揿下按钮/ 熄灭press the button / go out21．做一个噩梦/ 抓住你（两种）have a bad dream / get you, catch you22．完蛋（两种）be finished / be done for23．把山洞门开一点儿open the cave door a little24．跳着通过这狭窄的门口hopped through the narrow opening25．用手触摸袋鼠的脊背（两种）feel / touch their backs with his hands26．确定，确信（两种）make sure, be sure27．爬进这巨大袋鼠的口袋climbed into the giant kangaroo’s pocket28．击中，弄坏这个眼睛（两种）hit the eye , damage / destroy the eye29．立刻，马上（四种）immediately, at once, right now, at no time30．最后，终于（五种）at last, in the end, finally, lastly, eventually31．恐慌，害怕（四种）（过）panic / fear / be afraid / be frightened (panicked) 32．在船长花园里的一个人形 a figure in the captain’s garden33．悄悄地向房子靠近move silently towards the house34．这声音带领他的朋友们跑向他的门。
CCNA_EWAN_Chapter_7_答案
参加考试- EWAN Chapter 7 - CCNA Exploration: 接入WAN (版本 4.0)1主管要求技术人员在尝试排除NAT 连接故障之前总是要清除所有动态转换。
主管为什么提出这一要求？主管希望清除所有的机密信息，以免被该技术人员看见。
因为转换条目可能在缓存中存储很长时间，主管希望避免技术人员根据过时数据进行决策。
转换表可能装满，只有清理出空间后才能进行新的转换。
清除转换会重新读取启动配置，这可以纠正已发生的转换错误。
2请参见图示。
技术人员使用SDM 为一台Cisco 路由器输入了NAT 配置。
哪种说法正确描述了配置结果？内部用户会看到192.168.1.3 使用端口8080 发来了一个web 流量。
地址172.16.1.1 会被转换为以192.168.1.3 开头的地址池中的一个地址。
外部用户会看到192.168.1.3 使用端口80 发来了一个请求。
外部用户必须将流量发往端口8080 才能到达地址172.16.1.1。
3请参见图示。
R1 为网络10.1.1.0/24 执行NAT，R2 为网络192.168.1.2/24 执行NAT。
主机A 与网络服务器通信时，主机A 在其IP 报头中加的地址是什么？10.1.1.1172.30.20.2192.168.1.2255.255.255.2554网络管理员应该使用哪种NAT 来确保外部网络一直可访问内部网络中的web 服务器？NAT 过载静态NAT静态NATPAT5请参见图示。
流出R1 的流量转换失败。
最可能出错的是配置的哪个部分？ip nat pool语句access-list语句ip nat inside配置在错误的接口上接口s0/0/2 应该拥有一个私有IP 地址6网络管理员希望将两个IPv6 岛连接起来。
最简单的方式是通过仅使用IPv4 设备的公共网络来连接。
哪种简单的解决方案可解决此问题？将公共网络中的设备替换为支持IPv6 的设备。
国际金融Chapter 7
ANSWER:
A
4. If the interest rate is higher in the U.S. than in the United Kingdom, and if the forward rate of the British pound (in U.S. dollars) is the same as the pound’s spot rate, then: A) U.S. investors could possibly benefit from covered interest arbitrage. B) British investors could possibly benefit from covered interest arbitrage. C) neither U.S. nor British investors could benefit from covered interest arbitrage. D) U.S. and British investors could possibly benefit from covered interest arbitrage.
A) B)
C)
D)
As locational arbitrage occurs: the bid rate for pounds at Bank A will increase; the ask rate for pounds at Bank B will increase. the bid rate for pounds at Bank A will increase; the ask rate for pounds at Bank B will decrease. the bid rate for pounds at Bank A will decrease; the ask rate for pounds at Bank B will decrease. the bid rate for pounds at Bank A will decrease; the ask rate for pounds at Bank B will increase.
国际财务管理课后习题答案chapter 7doc资料
CHAPTER 7 FUTURES AND OPTIONS ON FOREIGN EXCHANGESUGGESTED ANSWERS AND SOLUTIONS TO END-OF-CHAPTERQUESTIONS AND PROBLEMSQUESTIONS1. Explain the basic differences between the operation of a currency forward market and a futures market.Answer: The forward market is an OTC market where the forward contract for purchase or sale of foreign currency is tailor-made between the client and its international bank. No money changes hands until the maturity date of the contract when delivery and receipt are typically made. A futures contract is an exchange-traded instrument with standardized features specifying contract size and delivery date. Futures contracts are marked-to-market daily to reflect changes in the settlement price. Delivery is seldom made in a futures market. Rather a reversing trade is made to close out a long or short position.2. In order for a derivatives market to function most efficiently, two types of economic agents are needed: hedgers and speculators. Explain.Answer: Two types of market participants are necessary for the efficient operation of a derivatives market: speculators and hedgers. A speculator attempts to profit from a change in the futures price. To do this, the speculator will take a long or short position in a futures contract depending upon his expectations of future price movement. A hedger, on-the-other-hand, desires to avoid price variation by locking in a purchase price of the underlying asset through a long position in a futures contract or a sales price through a short position. In effect, the hedger passes off the risk of price variation to the speculator who is better able, or at least more willing, to bear this risk.3. Why are most futures positions closed out through a reversing trade rather than held to delivery?Answer: In forward markets, approximately 90 percent of all contracts that are initially established result in the short making delivery to the long of the asset underlying the contract. This is natural because the terms of forward contracts are tailor-made between the long and short. By contrast, only about one percent of currency futures contracts result in delivery. While futures contracts are useful for speculation and hedging, their standardized delivery dates make them unlikely to correspond to the actual future dates when foreign exchange transactions will occur. Thus, they are generally closed out in a reversing trade. In fact, the commission thatbuyers and sellers pay to transact in the futures market is a single amount that covers the round-trip transactions of initiating and closing out the position.4. How can the FX futures market be used for price discovery?Answer: To the extent that FX forward prices are an unbiased predictor of future spot exchange rates, the market anticipates whether one currency will appreciate or depreciate versus another. Because FX futures contracts trade in an expiration cycle, different contracts expire at different periodic dates into the future. The pattern of the prices of these cont racts provides information as to the market’s current belief about the relative future value of one currency versus another at the scheduled expiration dates of the contracts. One will generally see a steadily appreciating or depreciating pattern; however, it may be mixed at times. Thus, the futures market is useful for price discovery, i.e., obtaining the market’s forecast of the spot exchange rate at different future dates.5. What is the major difference in the obligation of one with a long position in a futures (or forward) contract in comparison to an options contract?Answer: A futures (or forward) contract is a vehicle for buying or selling a stated amount of foreign exchange at a stated price per unit at a specified time in the future. If the long holds the contract to the delivery date, he pays the effective contractual futures (or forward) price, regardless of whether it is an advantageous price in comparison to the spot price at the delivery date. By contrast, an option is a contract giving the long the right to buy or sell a given quantity of an asset at a specified price at some time in the future, but not enforcing any obligation on him if the spot price is more favorable than the exercise price. Because the option owner does not have to exercise the option if it is to his disadvantage, the option has a price, or premium, whereas no price is paid at inception to enter into a futures (or forward) contract.6. What is meant by the terminology that an option is in-, at-, or out-of-the-money?Answer: A call (put) option with S t > E (E > S t) is referred to as trading in-the-money. If S t E the option is trading at-the-money. If S t< E (E < S t) the call (put) option is trading out-of-the-money.7. List the arguments (variables) of which an FX call or put option model price is a function. How does the call and put premium change with respect to a change in the arguments?Answer: Both call and put options are functions of only six variables: S t, E, r i, r$, T andσ. When all else remains the same, the price of a European FX call (put) option will increase:1. the larger (smaller) is S,2. the smaller (larger) is E,3. the smaller (larger) is r i,4. the larger (smaller) is r$,5. the larger (smaller) r$ is relative to r i, and6. the greater is σ.When r$ and r i are not too much different in size, a European FX call and put will increase in price when the option term-to-maturity increases. However, when r$ is very much larger than r i, a European FX call will increase in price, but the put premium will decrease, when the option term-to-maturity increases. The opposite is true when r i is very much greater than r$. For American FX options the analysis is less complicated. Since a longer term American option can be exercised on any date that a shorter term option can be exercised, or a some later date, it follows that the all else remaining the same, the longer term American option will sell at a price at least as large as the shorter term option.PROBLEMS1. Assume today’s settlement price on a CME EUR futures contract is $1.3140/EUR. You have a short position in one contract. Your performance bond account currently has a balance of $1,700. The next three day s’ settlement prices are $1.3126, $1.3133, and $1.3049. Calculate the changes in the performance bond account from daily marking-to-market and the balance of the performance bond account after the third day.Solution: $1,700 + [($1.3140 - $1.3126) + ($1.3126 - $1.3133)+ ($1.3133 - $1.3049)] x EUR125,000 = $2,837.50,where EUR125,000 is the contractual size of one EUR contract.2. Do problem 1 again assuming you have a long position in the futures contract.Solution: $1,700 + [($1.3126 - $1.3140) + ($1.3133 - $1.3126) + ($1.3049 - $1.3133)] x EUR125,000 = $562.50,where EUR125,000 is the contractual size of one EUR contract.With only $562.50 in your performance bond account, you would experience a margin call requesting that additional funds be added to your performance bond account to bring the balance back up to the initial performance bond level.3. Using the quotations in Exhibit 7.3, calculate the face value of the open interest in the June 2005 Swiss franc futures contract.Solution: 2,101 contracts x SF125,000 = SF262,625,000.where SF125,000 is the contractual size of one SF contract.4. Using the quotations in Exhibit 7.3, note that the June 2005 Mexican peso futures contract has a price of $0.08845. You believe the spot price in June will be $0.09500. What speculative position would you enter into to attempt to profit from your beliefs? Calculate your anticipated profits, assuming you take a position in three contracts. What is the size of your profit (loss) if the futures price is indeed an unbiased predictor of the future spot price and this price materializes?Solution: If you expect the Mexican peso to rise from $0.08845 to $0.09500, you would take a long position in futures since the futures price of $0.08845 is less than your expected spot price.Your anticipated profit from a long position in three contracts is: 3 x ($0.09500 - $0.08845) x MP500,000 = $9,825.00, where MP500,000 is the contractual size of one MP contract.If the futures price is an unbiased predictor of the expected spot price, the expected spot price is the futures price of $0.08845/MP. If this spot price materializes, you will not have any profits or losses from your short position in three futures contracts: 3 x ($0.08845 - $0.08845) x MP500,000 = 0.5. Do problem 4 again assuming you believe the June 2005 spot price will be $0.08500.Solution: If you expect the Mexican peso to depreciate from $0.08845 to $0.07500, you would take a short position in futures since the futures price of $0.08845 is greater than your expected spot price.Your anticipated profit from a short position in three contracts is: 3 x ($0.08845 - $0.07500) x MP500,000 = $20,175.00.If the futures price is an unbiased predictor of the future spot price and this price materializes, you will not profit or lose from your long futures position.6. George Johnson is considering a possible six-month $100 million LIBOR-based, floating-rate bank loan to fund a project at terms shown in the table below. Johnson fears a possible rise in the LIBOR rate by December and wants to use the December Eurodollar futures contract to hedge this risk. The contract expires December 20, 1999, has a US$ 1 million contract size, and a discount yield of7.3 percent.Johnson will ignore the cash flow implications of marking to market, initial margin requirements, and any timing mismatch between exchange-traded futures contract cash flows and the interest payments due in March.Loan TermsSeptember 20, 1999 December 20, 1999 March 20, 2000 • Borrow $100 million at • Pay interest for first three • Pay back principal September 20 LIBOR + 200 months plus interestbasis points (bps) • Roll loan over at• September 20 LIBOR = 7% December 20 LIBOR +200 bpsLoan First loan payment (9%) Second paymentinitiated and futures contract expires and principal↓↓↓•••9/20/99 12/20/99 3/20/00a. Formulate Johnson’s September 20 floating-to-fixed-rate strategy using the Eurodollar future contracts discussed in the text above. Show that this strategy would result in a fixed-rate loan, assuming an increase in the LIBOR rate to 7.8 percent by December 20, which remains at 7.8 percent through March 20. Show all calculations.Johnson is considering a 12-month loan as an alternative. This approach will result in two additional uncertain cash flows, as follows:Loan First Second Third Fourth payment initiated payment (9%) payment payment and principal ↓↓↓↓↓•••••9/20/99 12/20/99 3/20/00 6/20/00 9/20/00 b. Describe the strip hedge that Johnson could use and explain how it hedges the 12-month loan (specify number of contracts). No calculations are needed.CFA Guideline Answera. The basis point value (BPV) of a Eurodollar futures contract can be found by substituting the contract specifications into the following money market relationship:BPV FUT = Change in Value = (face value) x (days to maturity / 360) x (change in yield)= ($1 million) x (90 / 360) x (.0001)= $25The number of contract, N, can be found by:N = (BPV spot) / (BPV futures)= ($2,500) / ($25)= 100ORN = (value of spot position) / (face value of each futures contract)= ($100 million) / ($1 million)= 100ORN = (value of spot position) / (value of futures position)= ($100,000,000) / ($981,750)where value of futures position = $1,000,000 x [1 – (0.073 / 4)]102 contractsTherefore on September 20, Johnson would sell 100 (or 102) December Eurodollar futures contracts at the 7.3 percent yield. The implied LIBOR rate in December is 7.3 percent as indicated by the December Eurofutures discount yield of 7.3 percent. Thus a borrowing rate of 9.3 percent (7.3 percent + 200 basis points) can be locked in if the hedge is correctly implemented.A rise in the rate to 7.8 percent represents a 50 basis point (bp) increase over the implied LIBOR rate. For a 50 basis point increase in LIBOR, the cash flow on the short futures position is:= ($25 per basis point per contract) x 50 bp x 100 contracts= $125,000.However, the cash flow on the floating rate liability is:= -0.098 x ($100,000,000 / 4)= - $2,450,000.Combining the cash flow from the hedge with the cash flow from the loan results in a net outflow of $2,325,000, which translates into an annual rate of 9.3 percent:= ($2,325,000 x 4) / $100,000,000 = 0.093This is precisely the implied borrowing rate that Johnson locked in on September 20. Regardless of the LIBOR rate on December 20, the net cash outflow will be $2,325,000, which translates into an annualized rate of 9.3 percent. Consequently, the floating rate liability has been converted to a fixed rate liability in the sense that the interest rate uncertainty associated with the March 20 payment (using the December 20 contract) has been removed as of September 20.b. In a strip hedge, Johnson would sell 100 December futures (for the March payment), 100 March futures (for the June payment), and 100 June futures (for the September payment). The objective is to hedge each interest rate payment separately using the appropriate number of contracts. The problem is the same as in Part A except here three cash flows are subject to rising rates and a strip of futures is used to hedge this interest rate risk. This problem is simplified somewhat because the cash flow mismatch between thefutures and the loan payment is ignored. Therefore, in order to hedge each cash flow, Johnson simply sells 100 contracts for each payment. The strip hedge transforms the floating rate loan into a strip of fixed rate payments. As was done in Part A, the fixed rates are found by adding 200 basis points to the implied forward LIBOR rate indicated by the discount yield of the three different Eurodollar futures contracts. The fixed payments will be equal when the LIBOR term structure is flat for the first year.7. Jacob Bower has a liability that:• has a principal balance of $100 million on June 30, 1998,• accrues interest quarterly starting on June 30, 1998,• pays interest quarterly,• has a one-year term to maturity, and• calculates interest due based on 90-day LIBOR (the London Interbank OfferedRate).Bower wishes to hedge his remaining interest payments against changes in interest rates.Bower has correctly calculated that he needs to sell (short) 300 Eurodollar futures contracts to accomplish the hedge. He is considering the alternative hedging strategies outlined in the following table.Initial Position (6/30/98) in90-Day LIBOR Eurodollar ContractsStrategy A Strategy BContract Month (contracts) (contracts)September 1998 300 100December 1998 0 100March 1999 0 100a. Explain why strategy B is a more effective hedge than strategy A when the yield curveundergoes an instantaneous nonparallel shift.b. Discuss an interest rate scenario in which strategy A would be superior to strategy B.CFA Guideline Answera. Strategy B’s SuperiorityStrategy B is a strip hedge that is constructed by selling (shorting) 100 futures contracts maturing in each of the next three quarters. With the strip hedge in place, each quarter of the coming year is hedged against shifts in interest rates for that quarter. The reason Strategy B will be a more effective hedge than Strategy A for Jacob Bower is that Strategy B is likely to work well whether a parallel shift or a nonparallel shift occurs over the one-year term of Bower’s liability. That is, regardless of what happens to the term structure, Strategy B structures the futures hedge so that the rates reflected by the Eurodollar futures cash price match the applicable rates for the underlying liability-the 90day LIBOR-based rate on Bower’s liability. The same is not true for Strategy A. Because Jacob Bower’s liability carries a floating interest rate that resets quarterly, he needs a strategy that provides a series of three-month hedges. Strategy A will need to be restructured when the three-month September contract expires. In particular, if the yield curve twists upward (futures yields rise more for distant expirations than for near expirations), Strategy A will produce inferior hedge results.b. Scenario in Which Strategy A is SuperiorStrategy A is a stack hedge strategy that initially involves selling (shorting) 300 September contracts. Strategy A is rarely better than Strategy B as a hedging or risk-reduction strategy. Only from the perspective of favorable cash flows is Strategy A better than Strategy B. Such cash flows occur only in certain interest rate scenarios. For example Strategy A will work as well as Strategy B for Bower’s liability if interest rates (instantaneously) change in parallel fashion. Another interest rate scenario where Strategy A outperforms Strategy B is one in which the yield curve rises but with a twist so that futures yields rise more for near expirations than for distant expirations. Upon expiration of the September contract, Bower will have to roll out his hedge by selling 200 December contracts to hedge the remaining interest payments. This action will have the effect that the cash flow from Strategy A will be larger than the cash flow from Strategy B because the appreciation on the 300 short September futures contracts will be larger than the cumulative appreciation in the 300 contracts shorted in Strategy B (i.e., 100 September, 100 December, and 100 March). Consequently, the cash flow from Strategy A will more than offset the increase in the interest payment on the liability, whereas the cash flow from Strategy B will exactly offset the increase in the interest payment on the liability.8. Use the quotations in Exhibit 7.7 to calculate the intrinsic value and the time value of the 97 September Japanese yen American call and put options.Solution: Premium - Intrinsic Value = Time Value97 Sep Call 2.08 - Max[95.80 – 97.00 = - 1.20, 0] = 2.08 cents per 100 yen97 Sep Put 2.47 - Max[97.00 – 95.80 = 1.20, 0] = 1.27 cents per 100 yen9. Assume spot Swiss franc is $0.7000 and the six-month forward rate is $0.6950. What is the minimum price that a six-month American call option with a striking price of $0.6800 should sell for in a rational market? Assume the annualized six-month Eurodollar rate is 3 ½ percent.Solution:Note to Instructor: A complete solution to this problem relies on the boundary expressions presented in footnote 3 of the text of Chapter 7.C a≥Max[(70 - 68), (69.50 - 68)/(1.0175), 0]≥Max[ 2, 1.47, 0] = 2 cents10. Do problem 9 again assuming an American put option instead of a call option.Solution: P a≥Max[(68 - 70), (68 - 69.50)/(1.0175), 0]≥Max[ -2, -1.47, 0] = 0 cents11. Use the European option-pricing models developed in the chapter to value the call of problem 9 and the put of problem 10. Assume the annualized volatility of the Swiss franc is 14.2 percent. This problem can be solved using the FXOPM.xls spreadsheet.Solution:d1 = [ln(69.50/68) + .5(.142)2(.50)]/(.142)√.50 = .2675d2 = d1 - .142√.50 = .2765 - .1004 = .1671N(d1) = .6055N(d2) = .5664N(-d1) = .3945N(-d2) = .4336C e = [69.50(.6055) - 68(.5664)]e-(.035)(.50) = 3.51 centsP e = [68(.4336) - 69.50(.3945)]e-(.035)(.50) = 2.03 cents12. Use the binomial option-pricing model developed in the chapter to value the call of problem 9.The volatility of the Swiss franc is 14.2 percent.Solution: The spot rate at T will be either 77.39¢ = 70.00¢(1.1056) or 63.32¢ = 70.00¢(.9045), where u = e.142 .50 = 1.1056 and d = 1/u = .9045. At the exercise price of E = 68, the option will only be exercised at time T if the Swiss franc appreciates; its exercise value would be C uT= 9.39¢ = 77.39¢ - 68. If the Swiss franc depreciates it would not be rational to exercise the option; its value would be C dT = 0.The hedge ratio is h = (9.39 – 0)/(77.39 – 63.32) = .6674.Thus, the call premium is:C0 = Max{[69.50(.6674) – 68((70/68)(.6674 – 1) +1)]/(1.0175), 70 – 68}= Max[1.64, 2] = 2 cents per SF.MINI CASE: THE OPTIONS SPECULATORA speculator is considering the purchase of five three-month Japanese yen call options with a striking price of 96 cents per 100 yen. The premium is 1.35 cents per 100 yen. The spot price is 95.28 cents per 100 yen and the 90-day forward rate is 95.71 cents. The speculator believes the yen will appreciate to $1.00 per 100 yen over the next three months. As the speculator’s assistant, you have been asked to prepare the following:1. Graph the call option cash flow schedule.2. Determine the speculator’s profit if the yen appreciates to $1.00/100 yen.3. Determine the speculator’s profit if the yen only appreciates to the forward rate.4. Determine the future spot price at which the speculator will only break even.Suggested Solution to the Options Speculator:1.-2. (5 x ¥6,250,000) x [(100 - 96) - 1.35]/10000 = $8,281.25.3. Since the option expires out-of-the-money, the speculator will let the option expire worthless. He will only lose the option premium.4. S T = E + C = 96 + 1.35 = 97.35 cents per 100 yen.。
组合数学第五版第七章答案
1
0
1
9 34
0
1
2
··
·
·
·
··
·
·
·
The sequence repeats with period 3 (resp. 8) (resp. 6) if m = 2 (resp. m = 3) (resp. m = 4). The result follows.
4. For an integer n ≥ 5 we have
8. By construction h0 = 1 and h1 = 2. We now find hn for n ≥ 2. Consider a coloring of the 1 × n chessboard. The first square is colored red or blue. If it is blue, then there are hn−1 ways to color the remaining n − 1 squares. If it is red, then the second square is blue, and there are hn−2 ways to color the remaining n − 2 squares. Therefore hn = hn−1 + hn−2. Comparing the above data with the Fibonacci sequence we find hn = fn+2.
m = qn + r
1 ≤ r ≤ n − 1.
Observe that
GCD(n, r) = GCD(m, n) = d.
By induction and since r ≤ n − 1,
Chapter_7_Solutions
⎛ ⎜⎝1
−
(1
1 + r)6
⎞ ⎟⎠
+
⎛ ⎜⎝
(1
1 + r)6
⎞ ⎟⎠
300, 000 r
⎛ ⎜⎝1
−
(1
1 + r)10
⎞ ⎟⎠
=
−
200, 000 0.14
⎛ ⎜⎝1
−
1 (1.14)6
⎞ ⎟⎠
+
⎛ ⎜⎝
1 (1.14)6
⎞ ⎟⎠
300, 000 0.14
⎛ ⎜⎝1
−
1 (1.14)10
⎞ ⎟⎠
⎛1 ⎜⎝ 1 +
r
⎞ ⎟⎠
30 r
− 100
=
0
⇒
r
=
24.16%.
So, the cost of capital can be underestimated by 16.16% without changing the decision.
Evaluate: The NPV rule indicates that by making the investment, your factory will increase the value of the firm today by $4.885 million, so you should undertake the project. The IRR is the discount rate that sets the net present value of the cash flows equal to zero. The difference between the cost of capital and the IRR tells us the amount of estimation error in the cost of capital estimate that can exist without altering the original decision.
国际财务管理课后习题答案chapter-7
CHAPTER 7 FUTURES AND OPTIONS ON FOREIGN EXCHANGESUGGESTED ANSWERS AND SOLUTIONS TO END-OF-CHAPTERQUESTIONS AND PROBLEMSQUESTIONS1. Explain the basic differences between the operation of a currency forward market and a futures market.Answer: The forward market is an OTC market where the forward contract for purchase or sale of foreign currency is tailor-made between the client and its international bank. No money changes hands until the maturity date of the contract when delivery and receipt are typically made. A futures contract is an exchange-traded instrument with standardized features specifying contract size and delivery date. Futures contracts are marked-to-market daily to reflect changes in the settlement price. Delivery is seldom made in a futures market. Rather a reversing trade is made to close out a long or short position.2. In order for a derivatives market to function most efficiently, two types of economic agents are needed: hedgers and speculators. Explain.Answer: Two types of market participants are necessary for the efficient operation of a derivatives market: speculators and hedgers. A speculator attempts to profit from a change in the futures price. To do this, the speculator will take a long or short position in a futures contract depending upon his expectations of future price movement. A hedger, on-the-other-hand, desires to avoid price variation by locking in a purchase price of the underlying asset through a long position in a futures contract or a sales price through a short position. In effect, the hedger passes off the risk of price variation to the speculator who is better able, or at least more willing, to bear this risk.3. Why are most futures positions closed out through a reversing trade rather than held to delivery?Answer: In forward markets, approximately 90 percent of all contracts that are initially established result in the short making delivery to the long of the asset underlying the contract. This is natural because the terms of forward contracts are tailor-made between the long and short. By contrast, only about one percent of currency futures contracts result in delivery. While futures contracts are useful for speculation and hedging, their standardized delivery dates make them unlikely to correspond to the actual future dates when foreign exchange transactions will occur. Thus, they are generally closed out in a reversing trade. In fact, the commission thatbuyers and sellers pay to transact in the futures market is a single amount that covers the round-trip transactions of initiating and closing out the position.4. How can the FX futures market be used for price discovery?Answer: To the extent that FX forward prices are an unbiased predictor of future spot exchange rates, the market anticipates whether one currency will appreciate or depreciate versus another. Because FX futures contracts trade in an expiration cycle, different contracts expire at different periodic dates into the future. The pattern of the prices of these cont racts provides information as to the market’s current belief about the relative future value of one currency versus another at the scheduled expiration dates of the contracts. One will generally see a steadily appreciating or depreciating pattern; however, it may be mixed at times. Thus, the futures market is useful for price discovery, i.e., obtaining the market’s forecast of the spot exchange rate at different future dates.5. What is the major difference in the obligation of one with a long position in a futures (or forward) contract in comparison to an options contract?Answer: A futures (or forward) contract is a vehicle for buying or selling a stated amount of foreign exchange at a stated price per unit at a specified time in the future. If the long holds the contract to the delivery date, he pays the effective contractual futures (or forward) price, regardless of whether it is an advantageous price in comparison to the spot price at the delivery date. By contrast, an option is a contract giving the long the right to buy or sell a given quantity of an asset at a specified price at some time in the future, but not enforcing any obligation on him if the spot price is more favorable than the exercise price. Because the option owner does not have to exercise the option if it is to his disadvantage, the option has a price, or premium, whereas no price is paid at inception to enter into a futures (or forward) contract.6. What is meant by the terminology that an option is in-, at-, or out-of-the-money?Answer: A call (put) option with S t > E (E > S t) is referred to as trading in-the-money. If S t E the option is trading at-the-money. If S t< E (E < S t) the call (put) option is trading out-of-the-money.7. List the arguments (variables) of which an FX call or put option model price is a function. How does the call and put premium change with respect to a change in the arguments?Answer: Both call and put options are functions of only six variables: S t, E, r i, r$, T andσ. When all else remains the same, the price of a European FX call (put) option will increase:1. the larger (smaller) is S,2. the smaller (larger) is E,3. the smaller (larger) is r i,4. the larger (smaller) is r$,5. the larger (smaller) r$ is relative to r i, and6. the greater is σ.When r$ and r i are not too much different in size, a European FX call and put will increase in price when the option term-to-maturity increases. However, when r$ is very much larger than r i, a European FX call will increase in price, but the put premium will decrease, when the option term-to-maturity increases. The opposite is true when r i is very much greater than r$. For American FX options the analysis is less complicated. Since a longer term American option can be exercised on any date that a shorter term option can be exercised, or a some later date, it follows that the all else remaining the same, the longer term American option will sell at a price at least as large as the shorter term option.PROBLEMS1. Assume today’s settlement price on a CME EUR futures contract is $1.3140/EUR. You have a short position in one contract. Your performance bond account currently has a balance of $1,700. The next three day s’ settlement prices are $1.3126, $1.3133, and $1.3049. Calculate the changes in the performance bond account from daily marking-to-market and the balance of the performance bond account after the third day.Solution: $1,700 + [($1.3140 - $1.3126) + ($1.3126 - $1.3133)+ ($1.3133 - $1.3049)] x EUR125,000 = $2,837.50,where EUR125,000 is the contractual size of one EUR contract.2. Do problem 1 again assuming you have a long position in the futures contract.Solution: $1,700 + [($1.3126 - $1.3140) + ($1.3133 - $1.3126) + ($1.3049 - $1.3133)] x EUR125,000 = $562.50,where EUR125,000 is the contractual size of one EUR contract.With only $562.50 in your performance bond account, you would experience a margin call requesting that additional funds be added to your performance bond account to bring the balance back up to the initial performance bond level.3. Using the quotations in Exhibit 7.3, calculate the face value of the open interest in the June 2005 Swiss franc futures contract.Solution: 2,101 contracts x SF125,000 = SF262,625,000.where SF125,000 is the contractual size of one SF contract.4. Using the quotations in Exhibit 7.3, note that the June 2005 Mexican peso futures contract has a price of $0.08845. You believe the spot price in June will be $0.09500. What speculative position would you enter into to attempt to profit from your beliefs? Calculate your anticipated profits, assuming you take a position in three contracts. What is the size of your profit (loss) if the futures price is indeed an unbiased predictor of the future spot price and this price materializes?Solution: If you expect the Mexican peso to rise from $0.08845 to $0.09500, you would take a long position in futures since the futures price of $0.08845 is less than your expected spot price.Your anticipated profit from a long position in three contracts is: 3 x ($0.09500 - $0.08845) x MP500,000 = $9,825.00, where MP500,000 is the contractual size of one MP contract.If the futures price is an unbiased predictor of the expected spot price, the expected spot price is the futures price of $0.08845/MP. If this spot price materializes, you will not have any profits or losses from your short position in three futures contracts: 3 x ($0.08845 - $0.08845) x MP500,000 = 0.5. Do problem 4 again assuming you believe the June 2005 spot price will be $0.08500.Solution: If you expect the Mexican peso to depreciate from $0.08845 to $0.07500, you would take a short position in futures since the futures price of $0.08845 is greater than your expected spot price.Your anticipated profit from a short position in three contracts is: 3 x ($0.08845 - $0.07500) x MP500,000 = $20,175.00.If the futures price is an unbiased predictor of the future spot price and this price materializes, you will not profit or lose from your long futures position.6. George Johnson is considering a possible six-month $100 million LIBOR-based, floating-rate bank loan to fund a project at terms shown in the table below. Johnson fears a possible rise in the LIBOR rate by December and wants to use the December Eurodollar futures contract to hedge this risk. The contract expires December 20, 1999, has a US$ 1 million contract size, and a discount yield of7.3 percent.Johnson will ignore the cash flow implications of marking to market, initial margin requirements, and any timing mismatch between exchange-traded futures contract cash flows and the interest payments due in March.Loan TermsSeptember 20, 1999 December 20, 1999 March 20, 2000 • Borrow $100 million at • Pay interest for first three • Pay back principal September 20 LIBOR + 200 months plus interestbasis points (bps) • Roll loan over at• September 20 LIBOR = 7% December 20 LIBOR +200 bpsLoan First loan payment (9%) Second paymentinitiated and futures contract expires and principal↓↓↓•••9/20/99 12/20/99 3/20/00a. Formulate Johnson’s September 20 floating-to-fixed-rate strategy using the Eurodollar future contracts discussed in the text above. Show that this strategy would result in a fixed-rate loan, assuming an increase in the LIBOR rate to 7.8 percent by December 20, which remains at 7.8 percent through March 20. Show all calculations.Johnson is considering a 12-month loan as an alternative. This approach will result in two additional uncertain cash flows, as follows:Loan First Second Third Fourth payment initiated payment (9%) payment payment and principal ↓↓↓↓↓•••••9/20/99 12/20/99 3/20/00 6/20/00 9/20/00 b. Describe the strip hedge that Johnson could use and explain how it hedges the 12-month loan (specify number of contracts). No calculations are needed.CFA Guideline Answera. The basis point value (BPV) of a Eurodollar futures contract can be found by substituting the contract specifications into the following money market relationship:BPV FUT = Change in Value = (face value) x (days to maturity / 360) x (change in yield)= ($1 million) x (90 / 360) x (.0001)= $25The number of contract, N, can be found by:N = (BPV spot) / (BPV futures)= ($2,500) / ($25)= 100ORN = (value of spot position) / (face value of each futures contract)= ($100 million) / ($1 million)= 100ORN = (value of spot position) / (value of futures position)= ($100,000,000) / ($981,750)where value of futures position = $1,000,000 x [1 – (0.073 / 4)]102 contractsTherefore on September 20, Johnson would sell 100 (or 102) December Eurodollar futures contracts at the 7.3 percent yield. The implied LIBOR rate in December is 7.3 percent as indicated by the December Eurofutures discount yield of 7.3 percent. Thus a borrowing rate of 9.3 percent (7.3 percent + 200 basis points) can be locked in if the hedge is correctly implemented.A rise in the rate to 7.8 percent represents a 50 basis point (bp) increase over the implied LIBOR rate. For a 50 basis point increase in LIBOR, the cash flow on the short futures position is:= ($25 per basis point per contract) x 50 bp x 100 contracts= $125,000.However, the cash flow on the floating rate liability is:= -0.098 x ($100,000,000 / 4)= - $2,450,000.Combining the cash flow from the hedge with the cash flow from the loan results in a net outflow of $2,325,000, which translates into an annual rate of 9.3 percent:= ($2,325,000 x 4) / $100,000,000 = 0.093This is precisely the implied borrowing rate that Johnson locked in on September 20. Regardless of the LIBOR rate on December 20, the net cash outflow will be $2,325,000, which translates into an annualized rate of 9.3 percent. Consequently, the floating rate liability has been converted to a fixed rate liability in the sense that the interest rate uncertainty associated with the March 20 payment (using the December 20 contract) has been removed as of September 20.b. In a strip hedge, Johnson would sell 100 December futures (for the March payment), 100 March futures (for the June payment), and 100 June futures (for the September payment). The objective is to hedge each interest rate payment separately using the appropriate number of contracts. The problem is the same as in Part A except here three cash flows are subject to rising rates and a strip of futures is used to hedge this interest rate risk. This problem is simplified somewhat because the cash flow mismatch between thefutures and the loan payment is ignored. Therefore, in order to hedge each cash flow, Johnson simply sells 100 contracts for each payment. The strip hedge transforms the floating rate loan into a strip of fixed rate payments. As was done in Part A, the fixed rates are found by adding 200 basis points to the implied forward LIBOR rate indicated by the discount yield of the three different Eurodollar futures contracts. The fixed payments will be equal when the LIBOR term structure is flat for the first year.7. Jacob Bower has a liability that:• has a principal balance of $100 million on June 30, 1998,• accrues interest quarterly starting on June 30, 1998,• pays interest quarterly,• has a one-year term to maturity, and• calculates interest due based on 90-day LIBOR (the London Interbank OfferedRate).Bower wishes to hedge his remaining interest payments against changes in interest rates.Bower has correctly calculated that he needs to sell (short) 300 Eurodollar futures contracts to accomplish the hedge. He is considering the alternative hedging strategies outlined in the following table.Initial Position (6/30/98) in90-Day LIBOR Eurodollar ContractsStrategy A Strategy BContract Month (contracts) (contracts)September 1998 300 100December 1998 0 100March 1999 0 100a. Explain why strategy B is a more effective hedge than strategy A when the yield curveundergoes an instantaneous nonparallel shift.b. Discuss an interest rate scenario in which strategy A would be superior to strategy B.CFA Guideline Answera. Strategy B’s SuperiorityStrategy B is a strip hedge that is constructed by selling (shorting) 100 futures contracts maturing in each of the next three quarters. With the strip hedge in place, each quarter of the coming year is hedged against shifts in interest rates for that quarter. The reason Strategy B will be a more effective hedge than Strategy A for Jacob Bower is that Strategy B is likely to work well whether a parallel shift or a nonparallel shift occurs over the one-year term of Bower’s liability. That is, regardless of what happens to the term structure, Strategy B structures the futures hedge so that the rates reflected by the Eurodollar futures cash price match the applicable rates for the underlying liability-the 90day LIBOR-based rate on Bower’s liability. The same is not true for Strategy A. Because Jacob Bower’s liability carries a floating interest rate that resets quarterly, he needs a strategy that provides a series of three-month hedges. Strategy A will need to be restructured when the three-month September contract expires. In particular, if the yield curve twists upward (futures yields rise more for distant expirations than for near expirations), Strategy A will produce inferior hedge results.b. Scenario in Which Strategy A is SuperiorStrategy A is a stack hedge strategy that initially involves selling (shorting) 300 September contracts. Strategy A is rarely better than Strategy B as a hedging or risk-reduction strategy. Only from the perspective of favorable cash flows is Strategy A better than Strategy B. Such cash flows occur only in certain interest rate scenarios. For example Strategy A will work as well as Strategy B for Bower’s liability if interest rates (instantaneously) change in parallel fashion. Another interest rate scenario where Strategy A outperforms Strategy B is one in which the yield curve rises but with a twist so that futures yields rise more for near expirations than for distant expirations. Upon expiration of the September contract, Bower will have to roll out his hedge by selling 200 December contracts to hedge the remaining interest payments. This action will have the effect that the cash flow from Strategy A will be larger than the cash flow from Strategy B because the appreciation on the 300 short September futures contracts will be larger than the cumulative appreciation in the 300 contracts shorted in Strategy B (i.e., 100 September, 100 December, and 100 March). Consequently, the cash flow from Strategy A will more than offset the increase in the interest payment on the liability, whereas the cash flow from Strategy B will exactly offset the increase in the interest payment on the liability.8. Use the quotations in Exhibit 7.7 to calculate the intrinsic value and the time value of the 97 September Japanese yen American call and put options.Solution: Premium - Intrinsic Value = Time Value97 Sep Call 2.08 - Max[95.80 – 97.00 = - 1.20, 0] = 2.08 cents per 100 yen97 Sep Put 2.47 - Max[97.00 – 95.80 = 1.20, 0] = 1.27 cents per 100 yen9. Assume spot Swiss franc is $0.7000 and the six-month forward rate is $0.6950. What is the minimum price that a six-month American call option with a striking price of $0.6800 should sell for in a rational market? Assume the annualized six-month Eurodollar rate is 3 ½ percent.Solution:Note to Instructor: A complete solution to this problem relies on the boundary expressions presented in footnote 3 of the text of Chapter 7.C a≥Max[(70 - 68), (69.50 - 68)/(1.0175), 0]≥Max[ 2, 1.47, 0] = 2 cents10. Do problem 9 again assuming an American put option instead of a call option.Solution: P a≥Max[(68 - 70), (68 - 69.50)/(1.0175), 0]≥Max[ -2, -1.47, 0] = 0 cents11. Use the European option-pricing models developed in the chapter to value the call of problem 9 and the put of problem 10. Assume the annualized volatility of the Swiss franc is 14.2 percent. This problem can be solved using the FXOPM.xls spreadsheet.Solution:d1 = [ln(69.50/68) + .5(.142)2(.50)]/(.142)√.50 = .2675d2 = d1 - .142√.50 = .2765 - .1004 = .1671N(d1) = .6055N(d2) = .5664N(-d1) = .3945N(-d2) = .4336C e = [69.50(.6055) - 68(.5664)]e-(.035)(.50) = 3.51 centsP e = [68(.4336) - 69.50(.3945)]e-(.035)(.50) = 2.03 cents12. Use the binomial option-pricing model developed in the chapter to value the call of problem 9.The volatility of the Swiss franc is 14.2 percent.Solution: The spot rate at T will be either 77.39¢ = 70.00¢(1.1056) or 63.32¢ = 70.00¢(.9045), where u = e.142 .50 = 1.1056 and d = 1/u = .9045. At the exercise price of E = 68, the option will only be exercised at time T if the Swiss franc appreciates; its exercise value would be C uT= 9.39¢ = 77.39¢ - 68. If the Swiss franc depreciates it would not be rational to exercise the option; its value would be C dT = 0.The hedge ratio is h = (9.39 – 0)/(77.39 – 63.32) = .6674.Thus, the call premium is:C0 = Max{[69.50(.6674) – 68((70/68)(.6674 – 1) +1)]/(1.0175), 70 – 68}= Max[1.64, 2] = 2 cents per SF.MINI CASE: THE OPTIONS SPECULATORA speculator is considering the purchase of five three-month Japanese yen call options with a striking price of 96 cents per 100 yen. The premium is 1.35 cents per 100 yen. The spot price is 95.28 cents per 100 yen and the 90-day forward rate is 95.71 cents. The speculator believes the yen will appreciate to $1.00 per 100 yen over the next three months. As the speculator’s assistant, you have been asked to prepare the following:1. Graph the call option cash flow schedule.2. Determine the speculator’s profit if the yen appreciates to $1.00/100 yen.3. Determine the speculator’s profit if the yen only appreciates to the forward rate.4. Determine the future spot price at which the speculator will only break even.Suggested Solution to the Options Speculator:1.-2. (5 x ¥6,250,000) x [(100 - 96) - 1.35]/10000 = $8,281.25.3. Since the option expires out-of-the-money, the speculator will let the option expire worthless. He will only lose the option premium.4. S T = E + C = 96 + 1.35 = 97.35 cents per 100 yen.。
Chapter 7 课后答案
Chapter 7 答案Discourse Analysis1.Define the following terms briefly.(1)discourse: a general term for examples of language use, i.e. language producedas the result of an act of communication. It refers to the larger units oflanguage such as paragraphs, conversations and interviews.(2)discourse analysis: the study of how sentences in written and spoken languageform larger meaning units such as paragraphs, conversations and interviews.(3)given information: the information that the addresser believes is known to the addressee.(4)new information: the information that the addresser believes is not knownto the addressee.(5)topic: the main center of attention in a sentence.(6)cohesion: the grammatical and/or lexical relationships between the differentelements of a text. This may be the relationship between different sentencesor different parts of a sentence.(7)coherence: the relationship that links the meanings of utterances ina discourseor of the sentences in a text.(8)discourse marker: the technical term for all the items that are used to helpconstruct discourse, such as signifying the beginning or ending of a paragraphor a turn in conversation. They are commonly used in the initial positionof an utterance and are syntactically detachable from a sentence, such aswell, I mean, now, then, first, second, finally.(9)adjacency pair: a set of two consecutive, ordered turns that “go together” in aconversation, such as sequences of question/answer, greeting/greeting, invitation/acceptance, criticism/denial.(10) preference structure: in the conversations there can be several second partsrelated to one first part, but they are not of equal status. The structural likelihoodis called preference, and this likely structure is the preference structurethat divides second parts into preferred and dispreferred. The former is thestructurally expected and the latter unexpected. In answering the question“Have you got a light?”, the reply “Here you are” is preferred and “Sorry, no, I don’t smoke” is dispr eferred.(11 presequence: the opening sequences that are used to set up some special potentialactions, such as greetings before formal conversations. “What are youdoing tonight?” can be used as a presequence if it is followed by “If nothingspecial, come over and have dinner with us please.”(12) critical discourse analysis: the analysis of language use directed at, and committedto, discovering the concealed ideological bias, injustice, inequality in the power relations among speakers and hearers.2.In the study of discourse, cohesion refers to the grammatical and/or lexical relationshipsbetween the different parts of a text. This may be the relationship betweendifferent sentences or different parts of a sentence. It concerns the questionof how sentences are explicitly linked together in a discourse by different kinds ofovert devices. Such cohesive devices include reference, substitution, ellipses, conjunction and lexical cohesion.3.one→the look-out4.them (line 4)→plant and animal species (line 3)that (line 7)→“Every ecosystem everywhere can’t be preserved intact.”it (line 7)→“Every ecosystem everywhere can’t be preserved intact.”it (1st one, line 8)→how can it be made consistent with the earlier objective?it (2nd one, line 8)→to deprive some people in some parts of the world of a pieceof their ecosystem but not others.5.It is not a coherent discourse. Although it has connection words such as a Ford–– a car and black –– Black, which look like cohesive devices, they refer to entirelydifferent things. There is a total lack of internal relation among the sentences. Atext can’t be only based on superficial connections between the words to pursuecoherence; there must be some relationship that links the meanings of the sentencesin a text, too. This text is not in line with our real experience of the way theworld is. Thus, we can’t make sense of it directly unless we are laborious to createmeaningful connections which are not actually expressed by the words and sentences.So it’s not a coheren t discourse.6.Coherence is the relationship that links the meanings of utterances ina discourse or of the sentences in a text. This extract is coherent. All the sentences (questions in fact) are organized around the topic “interview”, and they are arrang ed from the general to the more specific in a logical order so that the text is easy to follow.。
伍德里奇计量经济学第六版答案Chapter 7
CHAPTER 7TEACHING NOTESThis is a fairly standard chapter on using qualitative information in regression analysis, although I try to emphasize examples with policy relevance (and only cross-sectional applications are included.).In allowing for different slopes, it is important, as in Chapter 6, to appropriately interpret the parameters and to decide whether they are of direct interest. For example, in the wage equation where the return to education is allowed to depend on gender, the coefficient on the female dummy variable is the wage differential between women and men at zero years of education. It is not surprising that we cannot estimate this very well, nor should we want to. In this particular example we would drop the interaction term because it is insignificant, but the issue of interpreting the parameters can arise in models where the interaction term is significant.In discussing the Chow test, I think it is important to discuss testing for differences in slope coefficients after allowing for an intercept difference. In many applications, a significant Chow statistic simply indicates intercept differences. (See the example in Section 7.4 on student-athlete GPAs in the text.) From a practical perspective, it is important to know whether the partial effects differ across groups or whether a constant differential is sufficient.I admit that an unconventional feature of this chapter is its introduction of the linear probability model. I cover the LPM here for several reasons. First, the LPM is being used more and more because it is easier to interpret than probit or logit models. Plus, once the proper parameter scalings are done for probit and logit, the estimated effects are often similar to the LPM partial effects near the mean or median values of the explanatory variables. The theoretical drawbacks of the LPM are often of secondary importance in practice. Computer Exercise C7.9 is a good one to illustrate that, even with over 9,000 observations, the LPM can deliver fitted values strictly between zero and one for all observations.If the LPM is not covered, many students will never know about using econometrics to explain qualitative outcomes. This would be especially unfortunate for students who might need to read an article where an LPM is used, or who might want to estimate an LPM for a term paper or senior thesis. Once they are introduced to purpose and interpretation of the LPM, along with its shortcomings, they can tackle nonlinear models on their own or in a subsequent course.A useful modification of the LPM estimated in equation (7.29) is to drop kidsge6 (because it is not significant) and then define two dummy variables, one for kidslt6 equal to one and the other for kidslt6 at least two. These can be included in place of kidslt6 (with no young children being the base group). This allows a diminishing marginal effect in an LPM. I was a bit surprised when a diminishing effect did not materialize.SOLUTIONS TO PROBLEMS7.1 (i) The coefficient on male is 87.75, so a man is estimated to sleep almost one and one-half hours more per week than a comparable woman. Further, t male = 87.75/34.33 ≈ 2.56, which is close to the 1% critical value against a two-sided alternative (about 2.58). Thus, the evidence for a gender differential is fairly strong.(ii) The t statistic on totwrk is -.163/.018 ≈ -9.06, which is very statistically significant. The coefficient implies that one more hour of work (60 minutes) is associated with .163(60) ≈ 9.8 minutes less sleep.(iii) To obtain 2r R , the R -squared from the restricted regression, we need to estimate themodel without age and age 2. When age and age 2 are both in the model, age has no effect only if the parameters on both terms are zero.7.2 (i) If ∆cigs = 10 then log()bwght ∆ = -.0044(10) = -.044, which means about a 4.4% lower birth weight.(ii) A white child is estimated to weigh about 5.5% more, other factors in the first equation fixed. Further, t white ≈ 4.23, which is well above any commonly used critical value. Thus, the difference between white and nonwhite babies is also statistically significant.(iii) If the mother has one more year of education, the child’s birth weight is estimated to be .3% higher. This is not a huge effect, and the t statistic is only one, so it is not statistically significant.(iv) The two regressions use different sets of observations. The second regression uses fewer observations because motheduc or fatheduc are missing for some observations. We would have to reestimate the first equation (and obtain the R -squared) using the same observations used to estimate the second equation.7.3 (i) The t statistic on hsize 2 is over four in absolute value, so there is very strong evidence that it belongs in the equation. We obtain this by finding the turnaround point; this is the value ofhsize that maximizes ˆsat(other things fixed): 19.3/(2⋅2.19) ≈ 4.41. Because hsize is measured in hundreds, the optimal size of graduating class is about 441.(ii) This is given by the coefficient on female (since black = 0): nonblack females have SAT scores about 45 points lower than nonblack males. The t statistic is about –10.51, so thedifference is very statistically significant. (The very large sample size certainly contributes to the statistical significance.)(iii) Because female = 0, the coefficient on black implies that a black male has an estimated SAT score almost 170 points less than a comparable nonblack male. The t statistic is over 13 in absolute value, so we easily reject the hypothesis that there is no ceteris paribus difference.(iv) We plug in black = 1, female = 1 for black females and black = 0 and female = 1 for nonblack females. The difference is therefore –169.81 + 62.31 = -107.50. Because the estimate depends on two coefficients, we cannot construct a t statistic from the information given. The easiest approach is to define dummy variables for three of the four race/gender categories and choose nonblack females as the base group. We can then obtain the t statistic we want as the coefficient on the black female dummy variable.7.4 (i) The approximate difference is just the coefficient on utility times 100, or –28.3%. The t statistic is -.283/.099 ≈ -2.86, which is very statistically significant.(ii) 100⋅[exp(-.283) – 1) ≈ -24.7%, and so the estimate is somewhat smaller in magnitude.(iii) The proportionate difference is .181 - .158 = .023, or about 2.3%. One equation that can be estimated to obtain the standard error of this difference islog(salary ) = 0β + 1βlog(sales ) + 2βroe + 1δconsprod + 2δutility +3δtrans + u ,where trans is a dummy variable for the transportation industry. Now, the base group is finance , and so the coefficient 1δ directly measures the difference between the consumer products and finance industries, and we can use the t statistic on consprod .7.5 (i) Following the hint, colGPA = 0ˆβ + 0ˆδ(1 – noPC ) + 1ˆβhsGPA + 2ˆβACT = (0ˆβ + 0ˆδ) - 0ˆδnoPC + 1ˆβhsGPA + 2ˆβACT . For the specific estimates in equation (7.6), 0ˆβ = 1.26 and 0ˆδ = .157, so the new intercept is 1.26 + .157 = 1.417. The coefficient on noPC is –.157.(ii) Nothing happens to the R -squared. Using noPC in place of PC is simply a different way of including the same information on PC ownership.(iii) It makes no sense to include both dummy variables in the regression: we cannot hold noPC fixed while changing PC . We have only two groups based on PC ownership so, in addition to the overall intercept, we need only to include one dummy variable. If we try toinclude both along with an intercept we have perfect multicollinearity (the dummy variable trap).7.6 In Section 3.3 – in particular, in the discussion surrounding Table 3.2 – we discussed how to determine the direction of bias in the OLS estimators when an important variable (ability, in this case) has been omitted from the regression. As we discussed there, Table 3.2 only strictly holds with a single explanatory variable included in the regression, but we often ignore the presence of other independent variables and use this table as a rough guide. (Or, we can use the results of Problem 3.10 for a more precise analysis.) If less able workers are more likely to receivetraining, then train and u are negatively correlated. If we ignore the presence of educ and exper , or at least assume that train and u are negatively correlated after netting out educ and exper , then we can use Table 3.2: the OLS estimator of 1β (with ability in the error term) has a downward bias. Because we think 1β ≥ 0, we are less likely to conclude that the training program waseffective. Intuitively, this makes sense: if those chosen for training had not received training, they would have lowers wages, on average, than the control group.7.7 (i) Write the population model underlying (7.29) asinlf = 0β + 1βnwifeinc + 2βeduc + 3βexper +4βexper 2 + 5βage+ 6βkidslt6 + 7βkidsage6 + u ,plug in inlf = 1 – outlf , and rearrange:1 – outlf = 0β + 1βnwifeinc + 2βeduc + 3βexper +4βexper2 + 5βage+ 6βkidslt6 + 7βkidsage6 + u ,oroutlf = (1 - 0β) - 1βnwifeinc - 2βeduc - 3βexper - 4βexper 2 - 5βage - 6βkidslt6 - 7βkidsage6 - u ,The new error term, -u , has the same properties as u . From this we see that if we regress outlf on all of the independent variables in (7.29), the new intercept is 1 - .586 = .414 and each slope coefficient takes on the opposite sign from when inlf is the dependent variable. For example, the new coefficient on educ is -.038 while the new coefficient on kidslt6 is .262.(ii) The standard errors will not change. In the case of the slopes, changing the signs of the estimators does not change their variances, and therefore the standard errors are unchanged (butthe t statistics change sign). Also, Var(1 - 0ˆβ) = Var(0ˆβ), so the standard error of the intercept is the same as before.(iii) We know that changing the units of measurement of independent variables, or entering qualitative information using different sets of dummy variables, does not change the R -squared. But here we are changing the dependent variable. Nevertheless, the R -squareds from the regressions are still the same. To see this, part (i) suggests that the squared residuals will be identical in the two regressions. For each i the error in the equation for outlf i is just the negative of the error in the other equation for inlf i , and the same is true of the residuals. Therefore, the SSRs are the same. Further, in this case, the total sum of squares are the same. For outlf we haveSST = 2211()[(1)(1)]n n i i i i outlf outlf inlf inlf ==-=---∑∑= 2211()()n ni i i i inlf inlf inlf inlf ==-+=-∑∑,which is the SST for inlf . Because R 2 = 1 – SSR/SST, the R -squared is the same in the two regressions.7.8 (i) We want to have a constant semi-elasticity model, so a standard wage equation with marijuana usage included would belog(wage ) = 0β + 1βusage + 2βeduc + 3βexper + 4βexper 2 + 5βfemale + u .Then 100⋅1β is the approximate percentage change in wage when marijuana usage increases byone time per month.(ii) We would add an interaction term in female and usage :log(wage ) = 0β + 1βusage + 2βeduc + 3βexper + 4βexper 2 + 5βfemale+ 6βfemale ⋅usage + u .The null hypothesis that the effect of marijuana usage does not differ by gender is H 0: 6β = 0.(iii) We take the base group to be nonuser. Then we need dummy variables for the other three groups: lghtuser , moduser , and hvyuser . Assuming no interactive effect with gender, the model would belog(wage ) = 0β + 1δlghtuser + 2δmoduser + 3δhvyuser + 2βeduc + 3βexper + 4βexper 2 + 5βfemale + u .(iv) The null hypothesis is H 0: 1δ = 0, 2δ= 0, 3δ = 0, for a total of q = 3 restrictions. If n is the sample size, the df in the unrestricted model – the denominator df in the F distribution – is n – 8. So we would obtain the critical value from the F q ,n -8 distribution.(v) The error term could contain factors, such as family background (including parental history of drug abuse) that could directly affect wages and also be correlated with marijuana usage. We are interested in the effects of a person’s drug usage on his or her wage, so we would like to hold other confounding factors fixed. We could try to collect data on relevant background information.7.9 (i) Plugging in u = 0 and d = 1 gives 10011()()()f z z βδβδ=+++.(ii) Setting **01()()f z f z = gives **010011()()z z βββδβδ+=+++ or *010z δδ=+. Therefore, provided 10δ≠, we have *01/z δδ=-. Clearly, *z is positive if and only if 01/δδ is negative, which means 01 and δδ must have opposite signs.(iii) Using part (ii) we have *.357/.03011.9totcoll == years.(iv) The estimated years of college where women catch up to men is much too high to be practically relevant. While the estimated coefficient on female totcoll ⋅ shows that the gap is reduced at higher levels of college, it is never closed – not even close. In fact, at four years of。
财务管理基础 第七章 课后题答案 斯坦利.B.布洛克
ChProblems1. City Farm Insurance has collection centers across the country to speed up collections. Thecompany also makes its disbursements from remote disbursement centers. The collection time has been reduced by two days and disbursement time increased by one day because of these policies. Excess funds are being invested in short-term instruments yielding12 percent per annum.a. If City Farm has $5 million per day in collections and $3 million per day indisbursements, how many dollars has the cash management system freed up?b. How much can City Farm earn in dollars per year on short-term investments madepossible by the freed-up cash?7-1. Solution:City Farm Insurancea. $5,000,000 daily collections× 2.0 days speed up = $10,000,000 additional collections$3,000,000 daily disbursements× 1.0 days slow down = $ 3,000,000 delayed disbursements$13,000,000 freed-up fundsb. $13,000,000 freed-up funds12% interest rate$1,560,000 interest on freed-up cash2. Nicholas Birdcage Company of Hollywood ships cages throughout the country. Nicholashas determined that through the establishment of local collection centers around thecountry, he can speed up the collection of payments by one and one-half days. Furthermore, the cash management department of his bank has indicated to him that he can defer hispayments on his accounts by one-half day without affecting suppliers. The bank has aremote disbursement center in Florida.a. If the company has $4 million per day in collections and $2 million per day indisbursements, how many dollars will the cash management system free up?b. If the company can earn 9 percent per annum on freed-up funds, how much will theincome be?c. If the annual cost of the new system is $700,000, should it be implemented?7-2. Solution:Nicholas Birdcage Company of Hollywooda. $4,000,000 daily collections× 1.5 days speed up = $6,000,000 additional collections$2,000,000 daily disbursements× .5 days slow down = $1,000,000 delayed disbursements$7,000,000 freed-up fundsb. $7,000,000 freed-up funds9% interest rate$630,000 interest on freed-up cashc. No. The annual income of $630,000 is $70,000 less than theannual cost of $700,000 for the new system.3. Megahurtz International Car Rentals has rent-a-car outlets throughout the world. It alsokeeps funds for transactions purposes in many foreign countries. Assume in 2003, it held 100,000 reals in Brazil worth 35,000 dollars. It drew 12 percent interest, but the Brazilian real declined 20 percent against the dollar.a. What is the value of its holdings, based on U.S. dollars, at year-end (Hint: multiply$35,000 times 1.12 and then multiply the resulting value by 80 percent.)b. What is the value of its holdings, based on U.S. dollars, at year-end if it drew9 percent interest and the real went up by 10 percent against the dollar?7-3. Solution:Megahurtz International Car Rentala. $35,000 × 1.12 = $39,200$39,200 × 80% = $31,360 dollar value of real holdingsb. $35,000 × 1.09 = $38,150$38,150 × 110% = $41,965 dollar value of real holdings4. Thompson Wood Products has credit sales of $2,160,000 and accounts receivableof $288,000. Compute the value of the average collection period.7-4. Solution:Thompson Wood ProductsAccounts Receivable Average collection period Average daily credit sales$288,000$2,160,000/360$288,00048days $6,000====5. Lone Star Petroleum Co. has annual credit sales of $2,880,000 and accounts receivableof $272,000. Compute the value of the average collection period.7-5. Solution:Lone Star Petroleum Co.Accounts Receivable Average collection period Average daily credit sales$272,000$2,288,000/360$272,0008,00034days ====6. Knight Roundtable Co. has annual credit sales of $1,080,000 and an average collectionperiod of 32 days in 2008. Assume a 360-day year. What is the company ’s averageaccounts receivable balance? Accounts receivable are equal to the average daily credit sales times the average collection period.7-6. Solution:Knight Roundtable Co.$1,080,000annual credit sales $3,000credit sales a day 360days per year=$3,000 average 32 average $96,000 average accounts daily credit sales collection period receivable balance=⨯7.Darla ’s Cosmetics has annual credit sales of $1,440,000 and an average collection period of 45 days in 2008. Assume a 360-day year.What is the company ’s average accounts receivable balance? Accounts receivable are equal to the average daily credit sales times the average collection period. 7-7. Solution:Darla ’s Cosmetic Company$1,440,000 annual credit sales/360 = $4,000 per day credit sales $4,000 credit sales × 45 average collection period = $180,000average accounts receivable balance8. In Problem 7, if accounts receivable change to $200,000 in the year 2009, while credit salesare $1,800,000, should we assume the firm has a more or a less lenient credit policy? 7-8. Solution:Darla ’s Cosmetics (Continued)To determine if there is a more lenient credit policy, compute the average collection period.Accounts ReceivableAverage collection period Average daily credit sales$200,000$1,800,000/360$200,00040 days $5,000====Since the firm has a shorter average collection period, it appears that the firm does not have a more lenient credit policy.9. Hubbell Electronic Wiring Company has an average collection period of 35 days. Theaccounts receivable balance is $105,000. What is the value of its credit sales?7-9. Solution:Hubbell Electronic Wiring CompanyAccounts receivable Average collection period Average daily credit sales$105,00035 days credit sales 360$105,000Credit sales/36035 daysCredit sales/360$3,000 credit sales per dayCredit sales $3,==⎛⎫ ⎪⎝⎭===000360$1,080,000⨯=10. Marv ’s Women ’s Wear has the following schedule for aging of accounts receivable.Age of Receivables, April 30, 2004(1)(2) (3) (4)Month of SalesAge of Account Amounts Percent of Amount Due April .................................0–30 $ 88,000 ____ March ...............................31–60 44,000 ____ February ...........................61–90 33,000 ____ January .............................91–120 55,000 ____ Total receivables ...........$220,000 100%a . Fill in column (4) for each month.b . If the firm had $960,000 in credit sales over the four-month period, compute the average collection period. Average daily sales should be based on a 120-day period.c . If the firm likes to see its bills collected in 30 days, should it be satisfied with the average collection period?d . Disregarding your answer to part c and considering the aging schedule for accounts receivable, should the company be satisfied? e . What additional information does the aging schedule bring to the company that theaverage collection period may not show?7-10. Solution:Marv’s Women’s WearAge of Receivables, April 30, 2004a.(1)(2)(3)(4)Month of SalesAge ofAccount AmountsPercent ofAmount DueApril 0-30 $ 88,000 40% March 31-60 44,000 20% February 61-90 33,000 15% January 91-120 55,000 25% Total receivables $220,000 100%b.Accounts receivable Average Collection PeriodAverage daily credit sales$220,000$960,000/120$220,000$8,00027.5 days====c. Yes, the average collection of 27.5 days is less than 30 days.d. No. The aging schedule provides additional insight that 60percent of the accounts receivable are over 30 days old.e. It goes beyond showing how many days of credit salesaccounts receivables represent, to indicate the distribution of accounts receivable between various time frames.11. Nowlin Pipe & Steel has projected sales of 72,000 pipes this year, an ordering cost of$6 per order, and carrying costs of $2.40 per pipe.a . What is the economic ordering quantity?b . How many orders will be placed during the year?c . What will the average inventory be?7-11. Solution:Nowlin Pipe and Steel Companya. EOQ 600 units =====b. 72,000 units/600 units = 120 ordersc. EOQ/2 = 600/2 = 300 units (average inventory)12. Howe Corporation is trying to improve its inventory control system and has installed anonline computer at its retail stores. Howe anticipates sales of 126,000 units per year, an ordering cost of $4 per order, and carrying costs of $1.008 per unit.a . What is the economic ordering quantity?b . How many orders will be placed during the year?c . What will the average inventory be?d . What is the total cost of inventory expected to be?7-12. Solution:Howe Corp.a. EOQ 1,000 units ===b. 126,000 units/1,000 units = 126 orders7-12. (Continued)c. EOQ/2 = 1,000/2 = 500 units (average inventory)d. 126 orders × $4 ordering cost= $ 504 500 units × $1.008 carrying cost per unit = 504 Total costs = $1,00813. (See Problem 12 for basic data.) In the second year, Howe Corporation finds it can reduceordering costs to $1 per order but that carrying costs will stay the same at $1.008 per unit. a . Recompute a, b, c , and d in Problem 12 for the second year.b . Now compare years one and two and explain what happened.7-13. Solution:Howe Corp. (Continued)a. EOQ 500 units =====126,000 units/500 units = 252 ordersEOQ/2 = 500/2 = 250 units (average inventory)252 orders × $1 ordering cost= $252 250 units × $1.008 carrying cost per unit = 252 Total costs = $504b. The number of units ordered declines 50%, while the numberof orders doubles. The average inventory and total costs both decline by one-half. Notice that the total cost did not decline in equal percentage to the decline in ordering costs. This isbecause the change in EOQ and other variables (½) isproportional to the square root of the change in orderingcosts (¼).14. Higgins Athletic Wear has expected sales of 22,500 units a year, carrying costs of $1.50per unit, and an ordering cost of $3 per order.a. What is the economic order quantity?b. What will be the average inventory? The total carrying cost?c. Assume an additional 30 units of inventory will be required as safety stock. What willthe new average inventory be? What will the new total carrying cost be?7-14. Solution:Higgins Athletic Weara. EOQ==300 units===b. EOQ/2 = 300/2 = 150 units (average inventory)150 units × $1.50 carrying cost/unit = $225 total carrying costc.EOQAverage inventory Safety Stock230030150301802=+=+=+= 180 inventory × $1.50 carrying cost per year = $270 total carrying cost15. Dimaggio Sports Equipment, Inc., is considering a switch to level production. Costefficiencies would occur under level production, and aftertax costs would decline by$35,000, but inventory would increase by $400,000. Dimaggio would have to finance the extra inventory at a cost of 10.5 percent.a. Should the company go ahead and switch to level production?b. How low would interest rates need to fall before level production would be feasible? 7-15. Solution:Dimaggio Sports Equipment, Inc.a. Inventory increases by $400,000× interest expense 10.5%Increased costs $ 42,000Less: Savings 35,000Loss ($ 7,000)Don’t switch to level production. Increased ROI is less thanthe interest cost of more inventory.b. If interest rates fall to 8.75% or less, the switch would befeasible.$35,000 Savings8.75%$400,000 increased inventory16. Johnson Electronics is considering extending trade credit to some customers previouslyconsidered poor risks. Sales will increase by $100,000 if credit is extended to these new customers. Of the new accounts receivable generated, 10 percent will prove to beuncollectible. Additional collection costs will be 3 percent of sales, and production and selling costs will be 79 percent of sales. The firm is in the 40 percent tax bracket.a. Compute the incremental income after taxes.b. What will Johnson’s incremental return on sales be if these new credit customers areaccepted?c. If the receivable turnover ratio is 6 to 1, and no other asset buildup is needed to servethe new customers, what will Johnson’s incremental return on new averageinvestment be?7-16. Solution:Johnson Electronicsa. Additional sales .................................................... $100,000Accounts uncollectible (10% of new sales) ......... – 10,000Annual incremental revenue ................................ $ 90,000Collection costs (3% of new sales) ...................... – 3,000Production and selling costs (79% of new sales) .– 79,000Annual income before taxes ................................. $ 8,000Taxes (40%) ......................................................... – 3,200Incremental income after taxes ............................ $ 4,800b.Incremental income Incremental return on salesIncremental sales$4,800/$100,000 4.8%===c. Receivable turnover = Sales/Receivable turnover = 6xReceivables = Sales/Receivable turnover= $100,000/6= $16,666.67Incremental return on new average investment =$4,800/$16,666.67 = 28.80%17. Collins Office Supplies is considering a more liberal credit policy to increase sales, butexpects that 9 percent of the new accounts will be uncollectible. Collection costs are5 percent of new sales, production and selling costs are 78 percent, and accounts receivableturnover is five times. Assume income taxes of 30 percent and an increase in sales of$80,000. No other asset buildup will be required to service the new accounts.a. What is the level of accounts receivable to support this sales expansion?b. What would be Collins’s incremental aftertax return on investment?c. Should Collins liberalize credit if a 15 percent aftertax return on investment isrequired?Assume Collins also needs to increase its level of inventory to support new sales and that inventory turnover is four times.d. What would be the total incremental investment in accounts receivable and inventoryto support a $80,000 increase in sales?e. Given the income determined in part b and the investment determined in part d,should Collins extend more liberal credit terms?7-17. Solution:Collins Office Suppliesa.$80,000 Investment in accounts receivable$16,0005==b. Added sales .......................................................... $ 80,000Accounts uncollectible (9% of new sales) ........... – 7,200 Annual incremental revenue ................................ $ 72,800 Collection costs (5% of new sales) ...................... – 4,000 Production and selling costs (78% of new sales) – 62,400 Annual income before taxes ................................. $ 6,400 Taxes (30%) ......................................................... – 1,920 Incremental income after taxes ............................ $ 4,480Return on incremental investment = $4,480/$16,000 = 28% c. Yes! 28% exceeds the required return of 15%.7-17. (Continued)d.$80,000 Investment in inventory =$20,0004Total incremental investmentInventory $20,000Accounts receivable 16,000Incremental investment $36,000 $4,480/$36,000 = 12.44% return on investmente. No! 12.44% is less than the required return of 15%.18. Curtis Toy Manufacturing Company is evaluating the extension of credit to a new group ofcustomers. Although these customers will provide $240,000 in additional credit sales,12 percent are likely to be uncollectible. The company will also incur $21,000 in additionalcollection expense. Production and marketing costs represent 72 percent of sales. Thecompany is in a 30 percent tax bracket and has a receivables turnover of six times. No other asset buildup will be required to service the new customers. The firm has a 10 percentdesired return on investment.a. Should Curtis extend credit to these customers?b. Should credit be extended if 14 percent of the new sales prove uncollectible?c. Should credit be extended if the receivables turnover drops to 1.5 and 12 percent ofthe accounts are uncollectible (as was the case in part a).Curtis Toy Manufacturing Companya. Added sales ............................................................. $240,000Accounts uncollectible (12% of new sales) ............ 28,800 Annual incremental revenue ................................... 211,200 Collection costs ....................................................... 21,000 Production and selling costs (72% of new sales) .... 172,800 Annual income before taxes .................................... 17,400 Taxes (30%) ............................................................ 5,220 Incremental income after taxes ............................... $ 12,180 $240,000Receivable turnover 6.0x 6.040,000 in new receivables ==$12,180Return on incremental investment 30.45%$40,000== b. Added sales ..........................................................$240,000 Accounts uncollectible (14% of new sales) .........– 33,600 Annual incremental revenue ................................$206,400 Collection costs ....................................................– 21,000 Production and selling costs (72% of new sales) .–172,800 Annual income before taxes .................................$ 12,600 Taxes (30%) .........................................................– 3,780 Incremental income after taxes ............................ $ 8,820$8,820Return on incremental investment 22.05%$40,000== Yes, extend credit.c. If receivable turnover drops to 1.5x, the investment inaccounts receivable would equal $240,000/1.5 = $160,000.The return on incremental investment, assuming a 12%uncollectible rate, is 7.61%.$12,180==Return on incremental investment7.61%$160,000The credit should not be extended. 7.61% is less than thedesired 10%.19. Reconsider problem 18. Assume the average collection period is 120 days. All other factorsare the same (including 12 percent uncollectibles). Should credit be extended?7-19. Solution:Curtis Toy Manufacturing Company (Continued) First compute the new accounts receivable balance.Accounts receivable = average collection period × average dailysales240,000120 days120$667$80,040⨯=⨯=360 daysorAccounts receivable = sales/accounts receivable turnover360 days==Accounts receivable turnover3x120 days=$240,000/3$80,000Then compute return on incremental investment.$12,18015.23%=$80,000Yes, extend credit. 15.23% is greater than 10%.20. Apollo Data Systems is considering a promotional campaign that will increase annualcredit sales by $600,000. The company will require investments in accounts receivable, inventory, and plant and equipment. The turnover for each is as follows:Accounts receivable (5x)Inventory (8x)Plant and equipment (2x)All $600,000 of the sales will be collectible. However, collection costs will be 3 percent of sales, and production and selling costs will be 77 percent of sales. The cost to carryinventory will be 6 percent of inventory. Depreciation expense on plant and equipment will be 7 percent of plant and equipment. The tax rate is 30 percent.a. Compute the investments in accounts receivable, inventory, and plant and equipmentbased on the turnover ratios. Add the three together.b. Compute the accounts receivable collection costs and production and selling costsand add the two figures together.c. Compute the costs of carrying inventory.d. Compute the depreciation expense on new plant and equipment.e. Add together all the costs in parts b, c, and d.f. Subtract the answer from part e from the sales figure of $600,000 to arrive at incomebefore taxes. Subtract taxes at a rate of 30 percent to arrive at income after taxes.g. Divide the aftertax return figure in part f by the total investment figure in part a. If thefirm has a required return on investment of 12 percent, should it undertake thepromotional campaign described throughout this problem.7-20. Solution:Apollo Data Systemsa. Accounts receivable = sales/accounts receivable turnover=$120,000$600,000/5Inventory = sales/inventory turnover=$75,000$600,000/8Plant and equipment = sales/(plant and equipment turnover)=$600,000/2$300,000Total investment$495,0007-20. (Continued)b. Collection cost = 3% × $600,000 $ 18,000Production and selling costs = 77% × $600,000 = 462,000Total costs related to accounts receivable $480,000c. Cost of carrying inventory6% × inventory6% × $75,000 $4,500d. Depreciation expense7% × Plant and Equipment7% × $300,000 $21,000e. Total costs related to accounts receivable $480,000Cost of carrying inventory 4,500Depreciation expense 21,000Total costs $505,500f. Sales $600,000– total costs 505,500Income before taxes 94,500Taxes (30%) 28,350Income after taxes $ 66,150g. Income after taxes$66,15013.36%Total investment495,000==Yes, it should undertake the campaignThe aftertax return of 13.36% exceeds the required rate of return of 12%21. In Problem 20, if inventory turnover had only been 4 times:a. What would be the new value for inventory investment?b. What would be the return on investment? You need to recompute the total investmentand the total costs of the campaign to work toward computing income after taxes.Should the campaign be undertaken?7-21. Solution:Apollo Data Systems (Continued)a. Inventory = sales/inventory turnover$150,000 = $600,000/4b. New Total InvestmentAccounts receivable $120,000Inventory 150,000Plant and equipment 300,000$570,000Total Cost of the CampaignCost of carrying inventory6% × $150,000 = $9,000 ($4,500 more than previously)New Income After TaxesSales $600,000– total costs 510,000 ($505,500 + 4,500)Income before taxes 90,000Taxes (30%) 27,000Income after taxes $ 63,000Income after taxes$63,000==11.05%Total investment570,000No, the campaign should not be undertakenThe aftertax return of 11.05% is less than the required rate ofreturn of 12%(Problems 22–25 are a series and should be taken in order.)22. Maddox Resources has credit sales of $180,000 yearly with credit terms of net 30 days,which is also the average collection period. Maddox does not offer a discount for early payment, so its customers take the full 30 days to pay.What is the average receivables balance? What is the receivables turnover?7-22. Solution:Maddox ResourcesSales/360 days = average daily sales$180,000/360 = $500Accounts receivable balance = $500 × 30 days = $15,000Receivable turnover =Sales$180,00012x Receivables$15,000==or360 days/30 = 12x23. If Maddox were to offer a 2 percent discount for payment in 10 days and every customertook advantage of the new terms, what would the new average receivables balance be?Use the full sales of $180,000 for your calculation of receivables.7-23. Solution:Maddox Resources (Continued)$500 × 10 days = $5,000 new receivable balance24. If Maddox reduces its bank loans, which cost 12 percent, by the cash generated from itsreduced receivables, what will be the net gain or loss to the firm?7-24. Solution:Maddox Resources (Continued)Old receivables – new receivables with discount = Funds freed by discount$15,000 – $5,000 ................................... = $10,000Savings on loan = 12% × $10,000 .......... = $ 1,200Discount on sales = 2% × $180,000 ........ = (3,600)Net change in income from discount ...... $(2,400) No! Don’t offer the discount since the income from reduced bankloans does not offset the loss on the discount.25. Assume that the new trade terms of 2/10, net 30 will increase sales by 20 percent becausethe discount makes the Maddox price competitive. If Maddox earns 16 percent on salesbefore discounts, should it offer the discount? (Consider the same variables as you did for problems 22 through 24.)7-25. Solution:Maddox Resources (Continued)New sales = $180,000 × 1.20 = $216,000 Sales per day = $216,000/360 = $600 Average receivables balance = $600 × 10 = $6,000 Savings in interest cost ($15,000 – $6,000) × 12% = 1,080 Increase profit on new sales = 16% × $36,000* = $5,760 Reduced profit because of discount = 2% × $216,000 = (4,320) Net change in income ............................................ $2,520 Yes, offer the discount because total profit increases.*New Sales $36,000 = $216,000 – $180,000COMPREHENSIVE PROBLEMBailey Distributing Company sells small appliances to hardware stores in the southern California area. Michael Bailey, the president of the company, is thinking about changing the credit policies offered by the firm to attract customers away from competitors. The current policy calls for a1/10, net 30, and the new policy would call for a 3/10, net 50. Currently 40 percent of Bailey customers are taking the discount, and it is anticipated that this number would go up to50 percent with the new discount policy. It is further anticipated that annual sales would increase from a level of $200,000 to $250,000 as a result of the change in the cash discount policy.The increased sales would also affect the inventory level. The average inventory carried by Bailey is based on a determination of an EOQ. Assume unit sales of small appliances will increase from 20,000 to 25,000 units. The ordering cost for each order is $100 and the carrying cost per unit is $1 (these values will not change with the discount). The average inventory is based on EOQ/2. Each unit in inventory has an average cost of $6.50.Cost of goods sold is equal to 65 percent of net sales; general and administrative expenses are 10 percent of net sales; and interest payments of 12 percent will be necessary only for the increase in the accounts receivable and inventory balances. Taxes will equal 25 percent of before-tax income.a. Compute the accounts receivable balance before and after the change in the cashdiscount policy. Use the net sales (Total sales – Cash discounts) to determine theaverage daily sales and the accounts receivable balances.b. Determine EOQ before and after the change in the cash discount policy. Translate thisinto average inventory (in units and dollars) before and after the change in the cashdiscount policy.c. Complete the income statement.Before Policy Change After Policy ChangeNet sales (Sales – Cash discounts)Cost of goods soldGross profitGeneral and administrativeexpenseOperating profitInterest on increase in accountsreceivable and inventory (12%)Income before taxesTaxesIncome after taxesd. Should the new cash discount policy be utilized? Briefly comment.Bailey Distributing Companya. Accounts receivable = average collection × averageperiod daily sales Before Policy ChangeAverage collection period .40 × 10 days = 4 .60 × 30 days = 18 22 days Average daily sales()()()$200,000.01.40$200,000Credit sales Discount 360360$200,000$800360$199,200360Average daily sales $553.33--=-===22 days × $553.33 = $12,173.26 accounts receivable before policy changeAfter Policy Change Average collection period .50 × 10 days = 5 .50 × 50 days = 25 30 days。
细胞生物学课后练习题及答案chapter7
第七章线粒体与叶绿体一、名词解释：1. 类囊体（thylakoid）2. 光合磷酸化（photophosphorylation）3. 半自主细胞器（semiautonomous organelle）4. 氧化磷酸化5. 呼吸链6. 细胞色素7. 捕光色素8. 质体醌9. 非循环光合磷酸化10. 光反应11. 暗反应二、选择题：请在以下每题中选出正确答案，每题正确答案为1-6个，多选和少选均不得分1. 以下哪一种情况有A TP合成A.用高钾低钠溶液浸泡细胞，然后转入低钾高钠溶液B.用酸性溶液浸泡亚线粒体颗粒，然后转入中性溶液C.用溶液碱性浸泡类囊体，然后转入中性溶液2. 叶绿体质子动力势的产生是因为A.膜间隙的pH值低于叶绿体基质的pH值B.膜间隙的pH值高于叶绿体基质的pH值C.内囊体腔的pH值低于叶绿体基质的pH值D.内囊体腔的pH值高于叶绿体基质的pH值3. 信号肽引导蛋白质进入线粒体、叶绿体之后，被信号肽酶切除，这种现象叫做A.co-translationB.post-translationC.co-transcriptionD.post-transcription4. 以下哪一种复合体能将蛋白质转运到线粒体膜间隙A.TOMC.TIM22D.OXA5. 绿色植物的细胞内存在几个遗传系统A.1B.2C.3D.46. 类囊体膜上电子传递的方向为A.PSI → PSII → NADP+B.PSI → NADP+ → PSIIC.PSI → PSII → H2OD.PSII → PSI → NADP+7. 植物光合作用释放的氧气来源于A.二氧化碳B.水分子8. 当植物在缺乏NADP+时，会发生A.循环式光合磷酸化B.非循环式光合磷酸化9. 光系统Ⅰ的中心色素为A.叶绿素bB.叶绿素aC.类胡萝卜素D.叶黄素10. 叶绿素是含有哪一类原子的卟啉衍生物A.Mn2+B.Mg2+C.Ca2+D.Fe2+11. 以下哪些复合物位于类囊体膜上B.光系统ⅡC.CF1-CF0D.细胞色素b6/f复合体12. 以下关于线粒体增殖的描述哪些是错误的A.线粒体来源于原有线粒体的分裂B.线粒体的分裂与细胞分裂同步C.细胞质中合成的蛋白质在信号序列的帮助下，被运入线粒体D.线粒体不能合成自身需要的蛋白质13. 细胞核的RNA聚合酶能被哪一种药物抑制A.放线菌素DB.溴化乙锭14. 线粒体的蛋白质合成能被哪一种药物抑制A.氯霉素B.放线菌酮15. 线粒体质子动力势的产生是因为膜间隙的pH值A.低于线粒体基质的pH值B.高于线粒体基质的pH值16. 2,4-二硝基酚(DNP) 抑制线粒体的A TP合成，因为它是一种A.质子载体B.质子通道C.是一种质子通道的阻断剂17. 寡霉素（oligomycin）抑制线粒体的ATP合成，因为它是一种A.质子载体B.质子通道C.质子通道的阻断剂18. 叠氮钠可抑制以下部位的电子传递A.NADH→CoQB.Cyt b→Cyt c1C.细胞色素氧化酶→O2。
chapter7
1练习九 恒定电流一、选择题1.室温下,铜导线内自由电子数密度n = 8.85⨯1028m -3,导线中电流密度j = 2⨯106A/m 2，则电子定向漂移速率为：(A) 1.4⨯10-4m/s. (B) 1.4⨯10-2m/s. (C) 5.4⨯102m/s. (D) 1.1⨯105m/s.2.在一个半径为R 1的导体球外面套一个与它共心的内半径为R 2的导体球壳,两导体的电导可以认为是无限大.在导体球与导体球壳之间充满电导率为γ的均匀导电物质,如图9.1所示.当在两导体间加一定电压时,测得两导体间电流为I , 则在两导体间距球心的距离为r 的P 点处的电场强度大小E 为：(A) I γ/(4πr 2) . (B) I /(4πγr 2) . (C) I /(4πγR 12) . (D) IR 22/(4πγR 12r 2) .3. 一平行板电容器极板间介质的介电常数为ε，电导率为γ，当极板上充电Q 时，则极板间的漏电流为(A) Q/(γε). (B) γε/Q . (C) εQ/γ. (D) γQ/ε .4.有一根电阻率为ρ、截面直径为d 、长度为L 的导线，若将电压U 加在该导线的两端，则单位时间内流过导线横截面的自由电子数为N ；若导线中自由电子数密度为n ，则电子平均漂移速度为v d . 下列哪个结论正确：(A) Lne U v Le Ud N d ρρπ==,42. (B) L ne U v ed LUN d ρπρ==,42.(C) LUnev Le Ud N d ρρπ==,82.图9.12(D) LUnev ed LUN d ρπρ==,42.5. 在氢放电管中充有气体，当放电管两极间加上足够高的电压时，气体电离. 如果氢放电管中每秒有4⨯1018个电子和1.5⨯1018个质子穿过放电管的某一截面向相反方向运动，则此氢放电管中的电流为(A) 0.40A . (B) 0.64A . (C) 0.88A . (D) 0.24A .二、 填空题1. 如图9.2所示为某复杂电路中的某节点,所设电流方向如图.则利用电流连续性列方程为 .2. 如图9.3所示为某复杂电路中的某回路,所设电流方向及回路中的电阻,电源如图.则利用基尔霍夫定律列方程为 .3. 有两个相同的电源和两个相同的电阻,按图9.4和图9.5所示两种方式连接. 在图9.3中I = ,U AB = ； 在图9.3中I = ,U AB = .三、计算题1. 把大地看作电阻率为ρ的均匀电介质,如图9.6.所示. 用一个半径为a 的球形电极与大地表面相接，半个球体埋在地面下，电极本身的电阻可忽略.求(1)电极的接地电阻；(2)当有电流流入大地时，距电极中心分别为r 1和r 2的两点A 、B 的电流密度j 1与j 2的比值.2. 一同轴电缆，长L = 1500m ，内导体外半径a = 1.0 mm ，外导体内半径b = 5.0 mm ，中间填充绝缘介质，由于电缆受潮，测得绝缘介质的电阻率降低到6.4⨯105Ω·m. 若信号源是电动势ε= 24V ，内阻r = 3.0Ω图9.2图9.3图9.4图9.5图9.63的直流电源. 求在电缆末端负载电阻R 0=1.0 k Ω上的信号电压为多大.练习十 磁感应强度 毕奥—萨伐尔定律一、选择题1. 如图10.1所示，边长为l 的正方形线圈中通有电流I ，则此线圈在A 点（如图）产生的磁感强度为:(A) l I πμ420. (B) l I πμ220. (C)lIπμ02(D) 以上均不对.2. 电流I 由长直导线1沿对角线AC 方向经A 点流入一电阻均匀分布的正方形导线框，再由D 点沿对角线BD 方向流出，经长直导线2返回电源, 如图10.2所示. 若载流直导线1、2和正方形框在导线框中心O 点产生的磁感强度分别用B 1、B 2和B 3表示，则O 点磁感强度的大小为:(A) B = 0. 因为 B 1 = B 2 = B 3 = 0 .(B) B = 0. 因为虽然B 1 ≠ 0, B 2 ≠ 0, B 1+B 2 = 0, B 3=0 (C) B ≠ 0. 因为虽然B 3 = 0, 但 B 1+B 2 ≠ 0 (D) B ≠ 0. 因为虽然B 1+B 2 = 0, 但 B 3 ≠ 03. 如图10.3所示，三条平行的无限长直导线，垂直通过边长为a 的正三角形顶点，每条导线中的电流都是I ，这三条导线在正三角形中心O(A) B = 0 .(B)B =3μ0I /(πa ) . (C) B =3μ0I /(2πa ) . (D) B =3μ0I /(3πa ) . . 4. 如图10.4所示，无限长直导线在P 处弯成半径为R 的圆，当通以电流I 时，则在圆心O 点的磁感强度大小等于：(A) R Iπμ20. (B)RI 40μ.图10.1图10.2图10.3图10.44(C) )11(20πμ-R I. (D) )11(40πμ+RI .5. 一匝数为N 的正三角形线圈边长为a ,通有电流为I , 则中心处的磁感应强度为 (A) B = 33μ0N I /(πa ) . (B) B =3μ0NI /(πa ) . (C) B = 0 .(D) B = 9μ0NI /(πa ) . 二、填空题1.平面线圈的磁矩为p m =IS n ，其中S 是电流为I 的平面线圈 , n 是平面线圈的法向单位矢量,按右手螺旋法则,当四指的方向代表 方向时,大拇指的方向代表 方向.2 两个半径分别为R 1、R 2的同心半圆形导线，与沿直径的直导线连接同一回路，回路中电流为I .(1) 如果两个半圆共面，如图10.5.a 所示，圆心O 点的磁感强度B 0的大小为 ，方向为 .(2) 如果两个半圆面正交，如图10.5b 所示，则圆心O 点的磁感强度B 0的大小为 ，B 0的方向与y 轴的夹角为 .3. 如图10.6所示,在真空中,电流由长直导线1沿切向经a 点流入一电阻均匀分布的圆环,再由b 点沿切向流出,经长直导线2返回电源.已知直导线上的电流强度为I ,圆环半径为R ，∠aob =180︒.则圆心O 点处的磁感强度的大小B = .三、计算题1. 如图10.7所示, 一宽为2a 的无限长导体薄片, 沿长度方向的电流I 在导体薄片上均匀分布. 求中心轴线OO '上方距导体薄片为a 的磁感强度.2. 如图10.8所示，半径为R 的木球上绕有密集的细导线，线圈图10.5图10.6b图10.85平面彼此平行，且以单层线圈覆盖住半个球面. 设线圈的总匝数为N ，通过线圈的电流为I . 求球心O 的磁感强度.练习十一 毕奥—萨伐尔定律(续) 磁场的高斯定理一、选择题1. 在磁感强度为B 的均匀磁场中作一半径为r 的半球面S ，S 边线所在平面的法线方向单位矢量n 与B 的夹角为θ，如图11.1所示. 则通过半球面S 的磁通量为：(A) πr 2B . (B) 2πr 2B . (C) -πr 2B sin θ.(D) -πr 2B cos θ. 2. 如图11.2所示，六根长导线互相绝缘，通过电流均为I ，区域Ⅰ、Ⅱ、Ⅲ、Ⅳ均为相等的正方形，哪个区域指向纸内的磁通量最大.(A) Ⅰ区域. (B) Ⅱ区域. (C) Ⅲ区域. (D) Ⅳ区域.(E) 最大不止一个区域.3. 如图11.3所示，有一无限大通有电流的扁平铜片，宽度为a ，厚度不计，电流I 在铜片上均匀分布，在铜片外与铜片共面，离铜片左边缘为b 处的P 点的磁感强度的大小为：(A) )(20b a I+πμ.(B) a b a bI+ln 20πμ. (C) bb a aI+ln20πμ. (D)])2/[(20b a I+πμ.4. 有一半径为R 的单匝圆线圈，通以电流I . 若将该导线弯成匝数N =2的平面圆线圈，导线长度不变，并通以同样的电流，则线圈中心的磁感强度和线圈的磁矩分别是原来的:(A) 4倍和1/2倍.(B) 4倍和1/8倍 . (C) 2倍和1/4倍 .(D) 2倍和 1/2倍 .5. 如图11.4,载流圆线圈(半径为R )与正方形线圈(边长为a )通有相同电流I ,若两线圈中心图11.1Ⅱ Ⅰ ⅢⅣ图11.2P图11.36O 1与O 2处的磁感应强度大小相同,则半径R 与边长a 之比R : a 为(A) 1:1.(B) π2:1. (C) π2:4. (D)π2:8二、填空题1. 一电子以速度v =1.0⨯107m/s 作直线运动，在与电子相距d =1.0⨯10-9m 的一点处，由电子产生的磁场的最大磁感强度B max = .2. 如图11.5,长为l 带电量为Q 的均匀带电直线平行于y 轴,在xy 平面内沿x 正向以速率v 运动,近端距x 轴也为l,当它运动到与y 轴重合时,坐标原点的磁感应强度B 的大小为 ,方向沿 .3.半径为R 的无限长圆筒形螺线管,在内部产生的是均匀磁场,方向沿轴线,与I 成右手螺旋;大小为μ0nI ,其中n 为单位长度上的线圈匝数,则通过螺线管横截面磁通量的大小为 .三、计算题1.在无限长直载流导线的右侧有面积为S 1和S 2的两个矩形回路, 回路旋转方向如图11.6所示, 两个回路与长直载流导线在同一平面内, 且矩形回路的一边与长直载流导线平行. 求通过两矩形回路的磁通量及通过S 1回路的磁通量与通过S 2回路的磁通量之比.2. 半径为R 的薄圆盘均匀带电，总电量为Q . 令此盘绕通过盘心且垂直盘面的轴线作匀速转动，角速度为ω，求轴线上距盘心x 处的磁感强度的大小和旋转圆盘的磁矩.练习十二 安培环路定律一、选择题1. 用相同细导线分别均匀密绕成两个单位长度匝数相等的半径为R 和r 的长直螺线管(R =2r )，螺线管长度远大于半径.今让两螺线管载有电流均为I ，则两螺线管中的磁感强度大小B R 和B r 应满足：(A) B R = 2B r . (B) B R = B r . (C) 2B R = B r . (D) B R = 4B r .2. 无限长直圆柱体，半径为R ，沿轴向均匀流有电流. 设圆柱体内(r < R )的磁感强度为图11.67B 1，圆柱体外(r >R )的磁感强度为B 2，则有：(A) B 1、B 2均与r 成正比. (B) B 1、B 2均与r 成反比. (C) B 1与r 成正比, B 2与r 成反比. (D) B 1与r 成反比, B 2与r 成正比.3. 在图12.1(a )和12.1(b )中各有一半径相同的圆形回路L 1和L 2，圆周内有电流I 2和I 2，其分布相同，且均在真空中，但在图12.1(b ）中，L 2回路外有电流I 3，P 1、P 2为两圆形回路上的对应点，则：(A) ⎰⋅1d L l B =⎰⋅2d L l B ,21P P B B =.(B) ⎰⋅1d L l B ≠⎰⋅2d L l B , 21P P B B =.(C) ⎰⋅1d L l B =⎰⋅2d L l B , 21P P B B ≠.(D)⎰⋅1d L l B ≠⎰⋅2d L l B ,21P P B B ≠.3. 无限长直圆柱体，半径为R ，沿轴向均匀流有电流. 设圆柱体内(r < R )的磁感强度为B 1，圆柱体外(r >R )的磁感强度为B 2，则有：(A) B 1、B 2均与r 成正比. (B) B 1、B 2均与r 成反比. (C) B 1与r 成正比, B 2与r 成反比. (D) B 1与r 成反比, B 2与r 成正比.4. 如图12.2所示，两根直导线ab 和cd 沿半径方向被接到一个截面处处相等的铁环上，恒定电流I 从a 端流入而从d 端流 出，则磁感强度B 沿图中闭合路径的积分⎰⋅Ll B d 等于：(A) μ0I . (B) μ0I /3. (C) μ0I /4. (D) 2μ0I /3 . 5. 如图12.3,在一圆形电流I 所在的平面内,选取一个同心圆形闭合回路L ,则由安培环路定理可知(A)0 d =⋅⎰L l B ,且环路上任意点B ≠0. (B) 0 d =⋅⎰Ll B ,且环路上任意点B =0.(C)0 d ≠⋅⎰Ll B ,且环路上任意点B ≠0.图12.1P 1(a )3 2 P2 (b )图12.28(D) 0 d ≠⋅⎰Ll B ,且环路上任意点B =0.二、填空题1.在安培环路定理中i LI ∑=⋅⎰0d μl B , 其中∑I i 是指 ;B 是指 ,B 是由环路的电流产生的.2. 两根长直导线通有电流I ,图12.3所示有三种环路, 对于环路a ,=⋅⎰a LlB d ;对于环路b , =⋅⎰bL l B d ;对于环路c , =⋅⎰cL l B d .3. 圆柱体上载有电流I ，电流在其横截面上均匀分布，一回路L 通过圆柱内部，将圆柱体横截面分为两部分，其面积大小分 别为S 1和S 2，如图12.4所示. 则=⋅⎰Ll B d .三、计算题1. 如图12.5所示，一根半径为R 的无限长载流直导体，其中电流I 沿轴向流过，并均匀分布在横截面上. 现在导体上有一半径为R '的圆柱形空腔，其轴与直导体的轴平行，两轴相距为 d . 试求空腔中任意一点的磁感强度.2. 设有两无限大平行载流平面,它们的电流密度均为j ,电流流向相反. 求：(1) 载流平面之间的磁感强度； (2) 两面之外空间的磁感强度.练习十三 安培力一、选择题1.有一由N 匝细导线绕成的平面正三角形线圈，边长为a , 通有电流I ，置于均匀外磁场B 中，当线圈平面的法向与外磁场同向时，该线圈所受的磁力矩M m 为:(A)3Na 2IB /2;图12.3图12.5(B) 3Na2IB/4;(C) 3Na2IB sin60︒ .(D) 0 .2. 如图13.1所示. 匀强磁场中有一矩形通电线圈，它的平面与磁场平行，在磁场作用下，线圈发生转动，其方向是：(A) ab边转入纸内，cd边转出纸外.(B) ab边转出纸外，cd边转入纸内.(C) ad边转入纸内，bc边转出纸外.(D) ad边转出纸外，cd边转入纸内.3. 若一平面载流线圈在磁场中既不受力，也不受力矩作用，这说明：(A) 该磁场一定不均匀，且线圈的磁矩方向一定与磁场方向平行.(B) 该磁场一定不均匀，且线圈的磁矩方向一定与磁场方向垂直.(C) 该磁场一定均匀，且线圈的磁矩方向一定与磁场方向平行.(D) 该磁场一定均匀，且线圈的磁矩方向一定与磁场方向垂直.4. 一张气泡室照片表明，质子的运动轨迹是一半径为10cm的圆弧，运动轨迹平面与磁感强度大小为0.3Wb·m2的磁场垂直. 该质子动能的数量级为(A) 0.01MeV.(B) 1MeV.(C) 0.1MeV.(D) 10Mev5. 一电子以速度v垂直地进入磁感强度为B的均匀磁场中，此电子在磁场中运动的轨道所围的面积内的磁通量是(A) 正比于B，反比于v2.(B) 反比于B，正比于v2.(C) 正比于B，反比于v.(D) 反比于B，反比于v.二、填空题1. 如图13.2所示, 在真空中有一半径为R的3/4圆弧形的导线, 其中通以稳恒电流I, 导线置于均匀外磁场中, 且B与导线所在平面平行.则该载流导线所受的大小为.2. 磁场中某点磁感强度的大小为2.0Wb/m2,在该点一圆形试验线圈所受的磁力矩为最大磁力矩6.28×10-6m⋅N,如果通过的电流为10mA,则可知线圈的半径为m,这时线圈平面法线方向与该处图13.2图13.1I910 磁场方向的夹角为 .3. 一半圆形闭合线圈, 半径R = 0.2m , 通过电流I = 5A , 放在均匀磁场中. 磁场方向与线圈平面平行, 如图13.3所示. 磁感应强度B = 0.5T. 则线圈所受到磁力矩为 . 若此线圈受磁力矩的作用从上述位置转到线圈平面与磁场方向成30︒的位置, 则此过程中磁力矩作功为 .三、计算题1. 一边长a =10cm 的正方形铜导线线圈(铜导线横截面积S =2.00mm 2, 铜的密度ρ=8.90g/cm 3), 放在均匀外磁场中. B 竖直向上, 且B = 9.40⨯10-3T, 线圈中电流为I =10A . 线圈在重力场中 求:(1) 今使线圈平面保持竖直, 则线圈所受的磁力矩为多少.(2) 假若线圈能以某一条水平边为轴自由摆动,当线圈平衡时,线圈平面与竖直面夹角为多少.2. 如图13.4所示，半径为R 的半圆线圈ACD 通有电流I 2, 置于电流为I 1的无限长直线电流的磁场中, 直线电流I 1 恰过半圆的直径, 两导线相互绝缘. 求半圆线圈受到长直线电流I 1的磁力.B图13.3I 图13.4练习9 恒定电流一、选择题 A B D A C 二、填空题1. I 1+ I 2+ I 3+ I 4=02. -ε1+ I 1r 1+ I 2R 1-ε2+ I 3r 2+ I 4R 2=03. ε/(R+r ), 0；0, ε.三、计算题1.(1)在距球心r 处沿电流方向取微元长度d r ,导电截面为2πr 2.则此微元长度电阻为 d R=ρd r/(2πr 2) 接地电阻为()[]⎰∞=adr r R 22πρ=ρ/(2πa )(2) j=I/S=I/(2πr 2)j 1/j 2=[I/(2πr 12)]/[I/(2πr 22)]= r 22/r 122. 其等效电路如图,R '为电缆漏电阻,其大小为()[]⎰='ba dr rl R πρ2=ρln(b/a )/(2πl )=109Ω 1/R=1/R '+1/R 0R=R 'R 0/(R '+R 0)=98.5Ω负载信号电压 V=V 0R/(R+r )=23.3V练习10 磁感应强度 毕奥—萨伐尔定律一、选择题 A A B C D 二、填空题1. 所围面积,电流,法线(n ).2. μ0I/(4R 1)+ μ0I/(4R 2),垂直向外;(μ0I/4)(1/R 12+1/R 22)1/2,π+arctan(R 1/R 2). 3. 0.三、计算题1.取宽为d x 的无限长电流元d I=I d x/(2a ) d B=μ0d I/(2πr ) =μ0I d x/(4πar )d B x =d B cos α=[μ0I d x/(4πar )](a/r )=μ0I d x/(4πr 2)= μ0I d x/[4π(x 2+a 2)] d B y =d B sin α= μ0Ix d x/[4πa (x 2+a 2)]()⎰⎰-+==a ax x a x xI B B 2204d d πμ =[μ0I/(4π)](1/a )arctan(x/a )a a-d I=μ0I/(8a ) ()⎰⎰-+==aay y ax a x Ix B B 2204d d πμ=[μ0I/(8πa )]ln(x 2+a 2)a a-=0d I=I d N=I [N/(πR/2)]R d θ 2. 取宽为d L 细圆环电流, =(2IN/π)d θd B=μ0d Ir 2/[2(r 2+x 2)3/2] r=R sin θ x=R cos θ d B=μ0NI sin 2θ d θ /(πR ) ⎰⎰==πππθθμ220d sin d RNI B B=μ0NI/(4R )练习11 毕—萨定律(续) 磁场的高斯定理一、选择题 D B C A D 二、填空题1. 0.16T.2. μ0Qv /(8πl 2), z 轴负向.3. μ0nI πR 2. 三、计算题1.取窄条面元d S =b d r , 面元上磁场的大小为 B =μ0I /(2πr ), 面元法线与磁场方向相反.有Φ1=⎰-=aabIbdr rI2002ln 2cos 2πμππμΦ2=⎰-=aabIbdr rI42002ln 2cos 2πμππμΦ1/Φ2=12. 在圆盘上取细圆环电荷元d Q =σ2πr d r , [σ=Q /(πR 2) ],等效电流元为d I =d Q /T =σ2πr d r/(2π/ω)=σωr d r(1)求磁场, 电流元在中心轴线上激发磁场的方向沿轴线,且与ω同向,大小为d B=μ0d Ir 2/[2(x 2+r 2)3/2]=μ0σωr 3d r /[2(x 2+r 2)3/2]()()()⎰⎰++=+=RRxrxr r xr r r B 02322222002/32230d 42d σωμσωμ =()()()⎰+++Rxrxrxr23222222d 4σωμ-()()⎰++Rxrxrx 023222220d 4σωμ=⎪⎪⎭⎫⎝⎛+++RRx r xx r 02222202σωμ =⎪⎪⎭⎫ ⎝⎛-++x xR x R RQ 222222220πωμ(2)求磁距. 电流元的磁矩 d P m =d IS=σωr d r πr 2=πσωr 2d r ⎰=Rm dr r P 03πσω=πσωR 4/4=ωQR 2/4练习12 安培环路定律一、选择题 B C C D A 二、填空题1. 环路L 所包围的电流, 环路L 上的磁感应强度,内外.2. μ0I , 0, 2μ0I .3. -μ0IS 1/(S 1+S 2),三、计算题1. 此电流可认为是由半径为R 的无限长圆柱电流I 1和一个同电流密度的反方向的半径为R '的无限长圆柱电流I 2组成.I 1=J πR 2 I 2=-J πR '2 J =I/[π (R 2-R '2)] 它们在空腔内产生的磁感强度分别为 B 1=μ0r 1J/2B 2=μ0r 2J/2 方向如图.有B x =B 2sin θ2-B 1sin θ1=(μ0J/2)(r 2sin θ2-r 1sin θ1)=0 ＋B 1cos θ1B y =B 2cos θ2=(μ0J/2)(r 2cos θ2＋r 1cos θ1)=(μ0J/2)d 所以 B= B y = μ0dI/[2π(R 2－R '2)] 方向沿y 轴正向2. 两无限大平行载流平面的截面如图.平面电流在空间产生的磁场为 B 1=μ0J /2在平面①的上方向右,在平面①的下方向左; 电流②在空间产生的磁场为 B 2=μ0J /2 在平面②的上方向左,在平面②的下方向右.(1) 两无限大电流流在平面之间产生的磁感强度方向都向左,故有 B=B 1+B 2=μ0J (2) 两无限大电流流在平面之外产生的磁感强度方向相反,故有 B=B 1-B 2=0 练习13 安培力一、选择题 D B C A B 二、填空题1 IBR .2 10－2, π/23 0.157N·m ; 7.85×10－2J .I 1I 2①②三、计算题1. (1) P m =IS=Ia 2方向垂直线圈平面. 线圈平面保持竖直,即P m 与B 垂直.有M m =P m ×BM m =P m B sin(π/2)=Ia 2B =9.4×10－4m ⋅N(2) 平衡即磁力矩与重力矩等值反向M m =P m B sin(π/2－θ)=Ia 2B cos θ M G = M G 1 + M G 2 + M G 3= mg (a/2)sin θ+ mga sin θ+ mg (a/2)sin θ =2(ρSa )ga sin θ=2ρSa 2g sin θ Ia 2B cos θ=2ρSa 2g sin θ tan θ=IB/(2ρSg )=0.2694θ=15︒2.在圆环上取微元 I 2d l = I 2R d θ 该处磁场为 B =μ0I 1/(2πR cos θ) I 2d l 与B 垂直,有d F= I 2d lB sin(π/2) d F=μ0I 1I 2d θ/(2πcos θ)d F x =d F cos θ=μ0I 1I 2d θ /(2π)d F y =d F sin θ=μ0I 1I 2sin θd θ /(2πcos θ)⎰-=222102πππθμd I I F x =μ0I 1I 2/2因对称F y =0.故 F =μ0I 1I 2/2 方向向右.I。
- 1、下载文档前请自行甄别文档内容的完整性，平台不提供额外的编辑、内容补充、找答案等附加服务。
- 2、"仅部分预览"的文档,不可在线预览部分如存在完整性等问题,可反馈申请退款(可完整预览的文档不适用该条件!)。
- 3、如文档侵犯您的权益，请联系客服反馈,我们会尽快为您处理(人工客服工作时间：9:00-18:30)。
第七章习题答案
7.1 ARM处理器有几种运行模式，处理器如何区别各种不同的运行模式？
ARM处理器有7中运行模式：
●用户模式（user）：ARM处理器正常的程序执行状态
●快速中断模式（fiq）：处理高速中断，用于高速数据传输或通道处理
●外部中断模式（irq）：用于普通的中断处理
●管理模式（supervisor）：操作系统使用的保护模式，系统复位后的默认模式
●中止模式（abort）：数据或指令预取中止时进入该模式
●未定义模式（undefined）：处理未定义指令，用于支持硬件协处理器的软件仿真
●系统模式（system）：运行特权级的操作系统任务
处理器使用CPSR寄存器中的M4~M0位来指示不同的运行模式。
7.2 通用寄存器中PC、CPSR和SPSR的作用各是什么？
PC：程序计数器，用于保存处理器要取的下一条指令的地址。
CPSR：当前程序状态寄存器，CPSR保存条件标志位、中断禁止位、当前处理器模式标志，以及其他一些相关的控制和状态位。
SPSR：备份程序状态寄存器，当异常发生时，SPSR用于保存CPSR的当前值，当从异常退出时，可用SPSR来恢复CPSR。
7.3 从编程的角度讲，ARM处理器的工作状态有哪两种？这两种状态之间如何转换？
从编程角度讲，ARM处理器的两种工作状态为：
●ARM状态（复位状态）：处理器执行32位的字对齐的ARM指令
●Thumb状态：处理器执行16位的半字对齐的Thumb指令
ARM指令集和Thumb指令集均有切换处理器状态的指令，并可在两种工作状态之间切换：
●进入Thumb状态：当操作数寄存器的状态位（最低位）为1时，执行BX指令就
可以进入Thumb状态。
如果处理器在Thumb状态时发生异常（异常处理要在ARM状态下执行），则当异常处理返回时自动切换到Thumb状态
●进入ARM状态：当操作数寄存器的状态位（最低位）位0时，执行BX指令就可
以进入ARM状态。
处理器进行异常处理时，把PC的值放入异常模式链接寄存器中，从异常向量地址开始执行程序，系统自动进入ARM状态
7.5 哪些特征是ARM和其他RISC体系结构所共有的？
ARM和其他RISC体系结构共有的三个相同特征：
●Load/Store体系结构：也称为寄存器/寄存器体系结构或RR系统结构。
在这类机
器中，操作数和运算结果不能直接从主寄存器中存取，而是必须借用大量的标量或矢量寄存器来进行中转。
采用这一结构的处理器必然要使用更多的通用寄存器存储操作数和运算结果，由于寄存器与运算器之间的数据传输速度远高于主存与运算器之间的数据传输速度，采用这一结构有助于提高计算机整体的运行速度
●采用固定长度精简指令集：这样使得机器译码变得容易，可以通过硬件直接译码
的方式完成对指令的解析。
虽然由于与复杂指令集相比，采用精简指令集需要更多指令来完成相同的任务，但采用硬件直接译码的速度却高于采用微码方式译码。
通过采用高速缓存等提高寄存器存储速度的技术，采用固定长度精简指令集的机器可以获得更高性能
●三地址指令格式：除了除法指令外，ARM的大部分数据处理指令采用三地址指
令。
即在指令中包含了目的操作数、源操作数和第二源操作数。