2011级国贸专业《微观经济学》作业及答案(B)

第1页SchoolofInternationalBusinessAdministration，ZISUSolutionstoAssignmentB(Note:AssignmentBshouldbefinishedandhandedinonMay23,2012)I.Interpretthefollowingtermsandconcepts.(5x3=15points)1.Monopoly:amarket(industry)withasingleproducerofagoodorservicethathasnoclosesubstituteandinwhichabarriertoentrypreventscompetitionfromnewfirms2.Marginalproduct:Theadditionaloutputthatcanbeproducedbyaddingonemoreunitofaspecificinput,ceterisparibus.3.Marginalcost:Theincreaseintotalcostthatresultsfromproducingonemoreunitofoutput.4.Constantreturnstoscale:Whenafirmincreasesitsplantsize(physicalcapital)andlaboremployedbythesamepercentage,andtheoutputincreasesbythesamepercentage,thenthefirm’saveragecostremainsconstantastheoutputincreases.5.Long-runaveragecostcurve:Thecurveshowsthelowestaveragecostatwhichafirmisabletoproduceeachoutputwhenthefirmisinlongrun(i.e.,afirmhashadsufficienttimetochangebothitsplantsizeanditslaboremployed.)II.Answerthefollowingquestionsbriefly.(4x5=20points)1.Whatarethecharacteristicsofaperfectlycompetitivemarket(industry)?Answer:alargenumberofsmallproducers(sellers)andbuyers,nobarrierstoentry,identicalproduct,wellknownmarketinformation.2.Explainbrieflythelawofdiminishingreturns.Answer:Whenadditionalunitsofavariableinputareaddedtofixedinputsafteracertainpoint,themarginalproductofthevariableinputdeclines.3.What’stherelationshipbetweenaveragetotalcostandmarginalcost?Answer:Ifmarginalcostisbelowaveragetotalcost,averagetotalcostwilldeclinetowardmarginalcost;ifmarginalcostisaboveaveragetotalcost,averagetotalcostwillincrease.4.Explainbrieflythedifferencebetweeneconomicprofitandaccountingprofit.Answer:Economicprofitequalstotalrevenueminuseconomiccost,i.e.,opportunitycost,whichisthesumofexplicitcostandimplicitcost,whileaccountingprofitequalstotalrevenueminusthesumofexplicitcostanddepreciation.Becausethedepreciationofcapitalisonlypartofimplicitcost,economicprofitisusuallylessthanaccountingprofit.III.Problemssolvedbycalculation(10+15+15+10=50points)1.Thenumberofrepairs(perweek)madebyacomputerrepairshopdependsonthenumberofworkers(perweek)asshowninfollowingtable.Assumethatallinputs(officespace,telephone,utilities)otherthanlaborarefixedintheshortrun.(10points)NumberofWorkers(PerWeek)01234567NumberofRepairs(PerWeek)08203545525760第2页a.Addtwoadditionalcolumnstothetable,andentermarginalproduct(MP)andaverageproduct(AP)foreachnumberofworkers.(4points)b.Overwhatrangeoflaborarethereincreasingreturnstolabor?Overwhatrangeoflaboraretherediminishingreturnstolabor?(2points)c.Overwhatrangeoflaborismarginalproductisgreaterthanaverageproduct?Whatishappeningtoaverageproductasemploymentincreasesoverthisrange?(2points)d.Overwhatrangeoflaborismarginalproductissmallerthanaverageproduct?Whatishappeningtoaverageproductasemploymentincreasesoverthisrange?(2points)Answer:(a)NumberofWorkers(PerWeek)01234567NumberofRepairs(PerWeek)08203545525760marginalproduct(MPL)-8121510753averageproduct(APL)-81011.6611.2510.409.508.57(b)Between1and3workers,thereareincreasingreturnstolabor(MPLincreasesasmoreworkersarehired).From3to7workerstherearediminishingreturnstolabor(MPLdecreasesasmoreworkersarehired).(c)Marginalproductisgreaterthanaverageproductforthesecondandthethirdworker,andaverageproductrisesasthesetwoworkersarehired.(d)Marginalproductislessthanaverageproductforthefourth,fifth,sixth,andseventhworkers.Aseachoftheseworkersishired,theaverageproductoflabordeclines.2.Acompetitivefirm’scostcurvesaregivenbythefollowingtable.(15points)QTCTFCTVCAVCATC(=AC)MC$$$$$$010010011301002150100316010041721005185100621010072401008280100933010010390100a.Completethetable.(3points)第3页b.GraphAVC,ATCandMConthesamegraph.WhatistherelationshipbetweentheMCandATC,andbetweentheMCandAVC?(3points)c.Supposethatmarketpriceis$30.Howmuchwillthecompetitivefirmproduceintheshortrun?Howmucharetotalprofits?(3points)d.Supposethatmarketpriceis$50.Howmuchwillthecompetitivefirmproduceintheshortrun?Howmucharetotalprofits?(3points)e.Supposethatmarketpriceis$10.Howmuchwillthecompetitivefirmproduceintheshortrun?Howmucharetotalprofits?(3points)Answer:a.QTCTFCTVCAVCATCMC$$$$$$01001000———11301003030130302150100502575203160100602053.3310417210072184312518510085173713621010011018.3352572401001402034.2930828010018022.503540933010023025.5636.665010390100290293960b.40$402AVC6820106080100q120130MCATCWhenMCislessthanATCAVC,ATCAVCisdecreasing.WhenMCismorethanATCAVC,ATCAVCisincreasing.WhenMCisequaltoATCAVC,ATCAVCisminimized.c.Thefirmwillproduce7unitsaccordingtoP=MC=$30formaximizingprofitandP＞AVC=$20.BecauseTR-TC=$30×7-$240=-$30,thefirmsuffersalossof$30.第4页d.Thefirmwillproduce9unitsaccordingtoP=MC=$50formaximizingprofitandP＞AVC=$25.56.BecauseTR-TC=$50×9-$330=$120,thefirmearnsaprofitof$120.e.AccordingtoP=MC=$10formaximizingprofit,thereexistsP＜AVC=$20,sothefirmshouldshutdownandincuronlyfixedcostsforatotallossof$100.3.Afirmcanusethreedifferentproductiontechnologies,withcapitalandlaborrequirementsateachlevelofoutputasfollows.(10points)DailyOutputTechnology1Technology2Technology3KLKLKL1003745541503104755200411