在习题1的基础上加入外国，其需求曲线为： D*= 80-20P，供给曲线为： S* =40+20P。a.推导并绘出外国

在习题1的基础上加入外国，其需求曲线为： D*= 80-20P，供给曲线为： S* =40+20P。

a.推导并绘出外国的出口供给曲线，同时计算没有贸易时外国的小麦价格。

b.如果本国和外国进行贸易，且运输成本为零。计算自由贸易时的均衡点，与之对应的世界价格是多少？贸易量又是多大？

Now add Foreign， which has a demand curve

D*=80-20P

and a supply curve

S*=40+20P

a. Derive and graph Foreign's export supply curve and find the price of wheat that would prevail in Foreign in the absence of trade.

b. Now allow Foreign and Home to trade with each other， at zero transportation cost. Find the equilibrium under free trade. What is the world price？ What is the volume of trade？