经济学原理曼昆课后答案chapter7.docx

经济学原理曼昆课后答案chapter7.docx

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经济学原理曼昆课后答案chapter7

i.

ProblemsandApplications

IfanearlyfreezeinCaliforniasoursthelemoncrop,thesupplycurveforlemonsshiftstotheleft,asshowninFigure7-5.Theresultisariseinthepriceoflemonsanda

declineinconsumersurplusfromA+B+CtojustA.Soconsumersurplusdeclines

bytheamountB+C.

JOOQ匸dP2巳

QuantityofLemons

Figure7-5

Inthemarketforlemonade,thehighercostoflemonsreducesthesupplyoflemonade,asshowninFigure7-6.TheresultisariseinthepriceoflemonadeandadeclineinconsumersurplusfromD+E+FtojustD,alossofE+F.Notethataneventthat

affectsconsumersurplusinonemarketoftenhaseffectsonconsumersurplusinothermarkets.

先ploPBUQLUa"!

joaoIJd

QuantityofLemonade

Figure7-6

2.AriseinthedemandforFrenchbreadleadstoanincreaseinproducersurplusinthe

marketforFrenchbread,asshowninFigure7-7.Theshiftofthedemandcurveleads

toanincreasedprice,whichincreasesproducersurplusfromareaAtoareaA+B+C.

pe會8IPLImlJ:

40

QiQs

QuantityofFrenchBread

Figure7-7

TheincreasedquantityofFrenchbreadbeingsoldincreasesthedemandforflour,asshowninFigure7-8.Asaresult,thepriceofflourrises,increasingproducersurplusfromareaDtoD+E+F.Notethataneventthataffectsproducersurplusinonemarketleadstoeffectsonproducersurplusinrelatedmarkets.

P2P1

Supply

QuantityofFlour

rt

e

B

rt

e

B

Figure7-8

sdemandscheduleis:

Price

QuantityDemanded

Morethan$7

0

$5to$7

1

$3to$5

2

$1to$3

3

$1orless

4

sdemandcurveisshowninFigure7-9.

1234

QuantityofWater

b.

c.

4.a.

Figure7-9

Whenthepriceofabottleofwateris$4,Bertbuystwobottlesofwater.His

consumersurplusisshownasareaAinthefigure.Hevalueshisfirstbottleof

waterat$7,butpaysonly$4forit,sohasconsumersurplusof$3.Hevalues

hissecondbottleofwaterat$5,butpaysonly$4forit,sohasconsumersurplusof$1.ThusBert'stotalconsumersurplusis$3+$1=$4,whichistheareaofAinthefigure.

Whenthepriceofabottleofwaterfallsfrom$4to$2,Bertbuysthreebottlesofwater,anincreaseofone.HisconsumersurplusconsistsofbothareasA

andBinthefigure,anincreaseintheamountofareaB.Hegetsconsumer

surplusof$5fromthefirstbottle（$7valueminus$2price）,$3fromthesecondbottle（$5valueminus$2price）,and$1fromthethirdbottle（$3valueminus$2price）,foratotalconsumersurplusof$9.Thusconsumersurplus

risesby$5（whichisthesizeofareaB）whenthepriceofabottleofwaterfallsfrom$4to$2.

Ernie'ssupplyscheduleforwateris:

Price

QuantitySupplied

Morethan$7

4

$5to$7

3

$3to$5

2

$1to$3

1

Lessthan$1

0

ErniessupplycurveisshowninFigure7-10.

$7-

6

5・B

4

3-r

A

2-

1

1234

QuantityofWater

b.

Figure7-10

Whenthepriceofabottleofwateris$4,Erniesellstwobottlesofwater.His

producersurplusisshownasareaAinthefigure.Hereceives$4forhisfirst

c.

bottleofwater,butitcostsonly$1toproduce,soErniehasproducersurplusof$3.Healsoreceives$4forhissecondbottleofwater,whichcosts$3toproduce,sohehasproducersurplusof$1.ThusErnie'stotalproducersurplusis$3+$1=$4,whichistheareaofAinthefigure.

Whenthepriceofabottleofwaterrisesfrom$4to$6,Erniesellsthreebottlesofwater,anincreaseofone.HisproducersurplusconsistsofbothareasAandBinthefigure,anincreasebytheamountofareaB.Hegetsproducer

surplusof$5fromthefirstbottle（$6priceminus$1cost）,$3fromthesecondbottle（$6priceminus$3cost）,and$1fromthethirdbottle（$6priceminus$5price）,foratotalproducersurplusof$9.Thusproducersurplusrisesby$5

5.a.

（whichisthesizeofareaB）whenthepriceofabottleofwaterrisesfrom$4to$6.

FromErnie'ssupplyscheduleandBert'sdemandschedule,thequantity

demandedandsuppliedare:

Price

QuantitySupplied

QuantityDemanded

$2

1

3

4

2

2

6

3

1

b.

Onlyapriceof$4bringssupplyanddemandintoequilibrium,withanequilibriumquantityof2.

c.

Atapriceof$4,consumersurplusis$4andproducersurplusis$4,asshowninproblems3and4.Totalsurplusis$4+$4=$8.

IfErnieproducedonefewerbottle,hisproducersurpluswoulddeclineto$3,asshowninproblem4.IfBertconsumedonefewerbottle,hisconsumer

surpluswoulddeclineto$3,asshowninproblem3.Sototalsurpluswould

d.

declineto$3+$3=$6.

IfErnieproducedoneadditionalbottleofwater,hiscostwouldbe$5,butthepriceisonly$4,sohisproducersurpluswoulddeclineby$1.IfBert

consumedoneadditionalbottleofwater,hisvaluewouldbe$3,butthepriceis$4,sohisconsumersurpluswoulddeclineby$1.Sototalsurplusdeclines

by$1+$1=$2.

6.

a.

Theeffectoffallingproductioncostsinthemarketforstereosresultsinashifttotherightinthesupplycurve,asshowninFigure7-11.Asaresult,the

b.

equilibriumpriceofstereosdeclinesandtheequilibriumquantityincreases.

ThedeclineinthepriceofstereosincreasesconsumersurplusfromareaAtoA

+B+C+D,anincreaseintheamountB+C+D.Priortotheshiftinsupply,

producersurpluswasareasB+E（theareaabovethesupplycurveandbelow

theprice）.Aftertheshiftinsupply,producersurplusisareasE+F+G.So

producersurpluschangesbytheamountF+G-B,whichmaybepositiveornegative.Theincreaseinquantityincreasesproducersurplus,whilethedeclineinthepricereducesproducersurplus.Sinceconsumersurplusrises

c.

byB+C+DandproducersurplusrisesbyF+G-B,totalsurplusrisesbyC+D+F+G.

Ifthesupplyofstereosisveryelastic,thentheshiftofthesupplycurvebenefitsconsumersmost.Totakethemostdramaticcase,supposethesupplycurvewerehorizontal,asshowninFigure7-12.Thenthereisno

producersurplusatall.Consumerscaptureallthebenefitsoffalling

productioncosts,withconsumersurplusrisingfromareaAtoareaA+B.

Figure7-11

see■科一S40oQud

Jos^£

Demand

QuantityofStereos

Figure7-12

7.Figure7-13showssupplyanddemandcurvesforhaircuts.Supplyequalsdemandat

aquantityofthreehaircutsandapricebetween$4and$5.FirmsA,C,andDshould

cutthehairofSallyJessy,Jerry,andMontel.Oprah'swillingnesstopayistoolowand

firmB'scostsaretoohigh,sotheydonotparticipate.Themaximumtotalsurplusistheareabetweenthedemandandsupplycurves,whichtotals$11（$8valueminus$2costforthefirsthaircut,plus$7valueminus$3costforthesecond,plus$5value

minus$4costforthethird）.

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$

MOIffiH2%'zd

llysysalJes

Jerry

Montel

B

C

A

Oprah

1234

QuantityofHaircuts

Figure7-13

8.a.Theeffectoffallingproductioncostsinthemarketforcomputersresultsina

shifttotherightinthesupplycurve,asshowninFigure7-14.Asaresult,the

equilibriumpriceofcomputersdeclinesandtheequilibriumquantityincreases.

ThedeclineinthepriceofcomputersincreasesconsumersurplusfromareaAtoA+B+C+D,anincreaseintheamountB+C+D.

Figure7-14

曹snduwo.0ss

Priortotheshiftinsupply,producersurpluswasareasB+E（theareaabovethesupplycurveandbelowtheprice）.Aftertheshiftinsupply,producer

surplusisareasE+F+G.SoproducersurpluschangesbytheamountF+G-B,whichmaybepositiveornegative.Theincreaseinquantityincreases

producersurplus,whilethedeclineinthepricereducesproducersurplus.

SinceconsumersurplusrisesbyB+C+DandproducersurplusrisesbyF+G-B,totalsurplusrisesbyC+D+F+G.

QqQi

QuantityofAddingMachines

Figure7-15

b.Sinceaddingmachinesaresubstitutesforcomputers,thedeclineintheprice

ofcomputersmeansthatpeoplesubstitutecomputersforaddingmachines,shiftingthedemandforaddingmachinestotheleft,asshowninFigure7-15.

Theresultisadeclineinboththeequilibriumpriceandequilibriumquantityofaddingmachines.Consumersurplusintheadding-machinemarketchanges

fromareaA+BtoA+C,anetgainofC-B.Producersurpluschangesfrom

areaC+D+EtoareaE,anetlossofC+D.Addingmachineproducersare

sadabouttechnologicaladvaneeincomputersbecausetheirproducersurplusdeclines.

c.Sincesoftwareandcomputersarecomplements,thedeclineinthepriceand

increaseinthequantityofcomputersmeansthatpeople'sdemandfor

softwareincreases,shiftingthedemandforsoftwaretotheright,asshowninFigure7-16.Theresultisanincreaseinboththepriceandquantityofsoftware.ConsumersurplusinthesoftwaremarketchangesfromB+CtoA+B,anetincreaseofA-C.ProducersurpluschangesfromEtoC+D+E,anincreaseofC+D,sosoftwareproducersshouldbehappyaboutthetechnologicalprogressincomputers.

d.Yes,thisanalysishelpsexplainwhyBillGatesisonetheworld'srichestm

sincehiscompanyproducesalotofsoftwarethat'sacomplementwith

computersandtherehasbeentremendoustechnologicaladvaneein

computers.

QiQw

QuantityofSoftware

Figure7-16

9.a.Figure7-17illustratesthedemandformedicalcare.Ifeachprocedurehasa

priceof$100,quantitydemandedwillbeQ1procedures.

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o

1

HWPQWJos^£

QiQ?

QuantityofMedicalProcedures

Figure7-17

b.Ifconsumerspayonly$20perprocedure,thequantitydemandedwil