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1.Demandcurveandsupplycurveandinterrelatedconceptsjustlikeelasticityofdemandandsupply.Demandcurve:Ineconomics,thedemandcurveisthegraphdepictingtherelationshipbetweenthepriceofacertaincommodity,andtheamountofitthatconsumersarewillingandabletopurchaseatthatgivenprice.Supplycurve:Agraphshowingthehypotheticalsupplyofaproductorservicethatwouldbeavailableatdifferentpricepoints.Elasticityistheratioofthepercentchangeinonevariabletothepercentchangeinanothervariable.Itisatoolformeasuringtheresponsivenessofafunctiontochangesinparametersinaunitlessway.Frequentlyusedelasticitiesincludepriceelasticityofdemand,priceelasticityofsupply,需求弹性Priceelasticityofdemand:PEDisameasureofresponsivenessofthequantityofagoodorservicedemandedtochangesinitsprice.Theformulaforthecoefficientofpriceelasticityofdemandforagoodis:Theaboveformulausuallyyieldsanegativevalue,duetotheinversenatureoftherelationshipbetweenpriceandquantitydemanded,Forexample,ifthepriceincreasesby5%andquantitydemandeddecreasesby5%,thentheelasticityattheinitialpriceandquantity=−5%/5%=−1.2.Theoryofutilityconsumertheory1)Utilityisameasureofrelativesatisfaction.2)LawofdiminishingmarginalutilityThemarginalutilityofeach(homogenous)unitdecreasesasthesupplyofunitsincreases3)Consumer’ssurplus:Consumersurplusisthedifferencebetweenthemaximumpriceaconsumeriswillingtopayandtheactualpricetheydopay4)Theproducersurplusistheamountthatproducersbenefitbysellingatamarketpricemechanismthatishigherthantheleastthattheywouldbewillingtosellfor.5)Attitudepeopletowardsrisks:riskavoidance,riskpreference,riskneutral6)AnEngelcurvedescribeshowhouseholdexpenditureonaparticulargoodorservicevarieswithhouseholdincome.3.Productiontheory1)ThetargetofafirmpursuesthemaximumofprofitIneconomics,returnstoscaleandeconomiesofscalearerelatedtermsthatdescribewhathappensasthescaleofproductionincreasesinthelongrun.Thetermreturnstoscalearisesinthecontextofafirm'sproductionfunction.Itreferstochangesinoutputresultingfromaproportionalchangeinallinputs.Ifoutputincreasesbythatsameproportionalchangethenthereareconstantreturnstoscale(CRS).Ifoutputincreasesbylessthanthatproportionalchange,therearedecreasingreturnstoscale(DRS).Ifoutputincreasesbymorethanthatproportionalchange,thereareincreasingreturnstoscale(IRS).Thusthereturnstoscalefacedbyafirmarepurelytechnologicallyimposedandarenotinfluencedbyeconomicdecisionsorbymarketconditions.Economiesofscale:isalongrunconceptandreferstoreductionsinunitcostasthesizeofafacilityandtheusagelevelsofotherinputsincrease.Thecommonsourcesofeconomiesofscalearepurchasing(bulkbuyingofmaterialsthroughlong-termcontracts),managerial(increasingthespecializationofmanagers),andtechnological(takingadvantageofreturnstoscaleintheproductionfunction).Eachofthesefactorsreducesthelongrunaveragecosts(LRAC)ofproductionEconomiesofscalerefertoafirm'scosts;returnstoscaledescribetherelationshipbetweeninputsandoutputsinalong-runproduction.Costtheory:1)Opportunitycost:Itiskindofsacrificerelatedtotheotherbestchoiceavailabletopeoplewhohadseveralmutuallyexclusivechoices.Economicprofit:Afirmissaidtobemakinganeconomicprofitwhenitsaveragetotalcostislessthanthepriceofeachadditionalproductattheprofit-maximizingoutput.Theeconomicprofitisequaltothequantityoutputmultipliedbythedifferencebetweentheaveragetotalcostandtheprice.Normalprofit=cost:Afirmissaidtobemakinganormalprofitwhenitseconomicprofitequalszero.Perfectcompetitivemarket;monopolisticcompetitionmarket;monopolisticmarket;oligopolisticmarket.Pricediscrimination：Whensalesofidenticalgoodsorservicesaretransactedatdifferentpricesfromthesameprovider.Pricediscriminationcanonlybeafeatureofmonopolisticandoligopolisticmarkets,Marketfailure:aconceptwithineconomictheorythattheallocationofgoodsandservicesbyafreemarketisnotefficient.Marketfailuresareoftenassociatedwithinformationasymmetries,Monopolies,externalities,orpublicgoods.Theexistenceofamarketfailureisoftenusedasajustificationforgovernmentinterventioninaparticularmarket.However,sometypesofgovernmentpolicyinterventions,suchastaxes,subsidies,wageandpricecontrols,andregulations,includingattemptstocorrectmarketfailure,mayalsoleadtoaninefficientallocationofresources,(sometimescalledgovernmentfailures).Thus,thereissometimesachoicethatwhetherusesgovernmentinterventionwhenmarketfailuresoccur.Externalities:Theactionsofagentscanhaveexternalities,whichareinnatetothemethodsofproduction.Forexample,ifafirmisproducingsteel,itpollutestheatmospherewhenitmakessteel,however,andifitisnotforcedtopayfortheuseofthisresource,thenthiscostwillbebornenotbythefirmbutbysociety.Commonexamplesofanexternalityisenvironmentalharmsuchaspollutionoroverexploitationofnaturalresources.Monopolies:Agentsinamarketcangainmarketpower,allowingthemtoblockothermutuallybeneficialgainsfromtradesfromoccurring.Inamonopoly,themarketequilibriumwillnolongerbeParetooptimal.Themonopolywilluseitsmarketpowertorestrictoutputbelowthequantityatwhichthemarginalsocialbenefitisequaltothemarginalsocialcostofthelastunitproduced,soastokeeppricesandprofitshigh.Informationasymmetrydealswiththe