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.
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:
Figure7-9
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
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
87654321
$
MOIffiH2%'zd
llysysalJes
Jerry
Montel
B
C
A
Oprah
minus$4costforthethird）.
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
o
o
1
HWPQWJos^£
priceof$100,quantitydemandedwillbeQ1procedures.
QiQ?
QuantityofMedicalProcedures
Figure7-17
b.Ifconsumerspayonly$20perprocedure,thequantitydemandedwillbeQ2
procedures.Sincethe
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