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Chapter 2
1．Home has 1200 units of labor available. It can produce two goods, apples and bananas. The unit labor requirement in apple production is 3, while in banana production it is 2.
a．Graph out the production possibilities frontier:
Home's PPF
Qbanana 800600
400 2000
200400600800Qapple
b．What is the opportunity cost of apples in terms of bananas?
aLa?1.5 aLbc．In the absence of trade, what would the price of apples in terms of bananas be?
In the absence of trade, since labor is the only factor of production and supply
decisions are determined by the attempts of individuals to maximize their
earnings in a competitive economy, only when Pa/Pb ? aLa/aLbwill both goods be produced. So Pa/Pb ? 1.5
2．Home is as described in problem 1. There is now also another country, Foreign,
with a labor force of 800. Foreign’s unit labor requirement in apple production is 5, while in banana production it is 1.
a．Graph Foreign’s production possibilities frontier: Foreign's PPF Q*banana 1000800
600
400
200
0
Q*apple80160240320400
b．Construct the world relative supply curve. 1 / 71
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3．Now suppose world relative demand takes the following form: Demand for apples/demand for bananas = price of bananas/price of apples.
a．Graph the relative demand curve along with the relative supply curve: Da/Db?Pb/Pa
DaQa?Q?aPa?1 ∵When the market achieves its equilibrium, we have ??() ?DbQb?QbPb∴RD is a hyperbola y?1 x
b．What is the equilibrium relative price of apples?
The equilibrium relative price of apples is determined by the intersection
of the RD and RS curves. RD: x?1 y?x?[0,0.5)? RS: ?x?0.5?x?(0.5,??]? ∴x?0.5
y?1.5y?[1.5,5] y?5y?22 / 72
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∴Pea/Peb?2
c．Describe the pattern of trade. ∵P?a/P?b?Pea/Peb?Pa/Pb
∴In this two-country world, Home will specialize in the apple production, export apples and import bananas. Foreign will specialize in the banana production, export bananas and import apples. d．Show that both Home and Foreign gain from trade.
International trade allows Home and Foreign to consume anywhere within the
colored lines, which lie outside the countries’ production possibility frontiers. And the indirect method, specializing in producing only one production then trade with other country, is a more efficient method than direct production. In the absence of trade, Home could gain three bananas by foregoing two apples, and Foreign could gain by one foregoing five bananas. Trade allows each country to trade two bananas for one apple. Home could then gain four bananas by foregoing two apples while Foreign could gain one apple by foregoing only two bananas. So both Home and Foreign gain from trade. 4．Suppose that instead of 1200 workers, Home had 2400. Find the equilibrium relative price. What can you say about the efficiency of world production and the division of the gains from trade between Home and Foreign in this case?
RD: x?1 y?x?[0,1)? RS: ?x?1?x?(1,??]? ∴x?y?1.5y?[1.5,5] y?523y?1.5
ee ∴Pa/Pb?1.5 3 / 73
克鲁格曼国际经济学答案
