1.If the cross-price elasticity of the demand for type- writers with respect to the price of computers is 0.25, the own price elasticity of demand for typewriters is -0.5, and the price elasticity of the supply of typewriters is 1.0, how much would the price and quantity of typewriters exchanged change if computers became 20 percent cheaper? 答案: 价格跟数量都下跌1/30 这要怎麽算，而且价格下跌数量也跟着下跌?? 2.假设在 two- market system 中 Ex 和 Ey 分别为物品 X 和 Y 的超 额需求，Ex = 100 -5Px +Py， Ey = 50 +2Px -2Py, 则 a.X 和 Y 二者是 gross substitutes b.X 和 Y二者是 gross complements c.X 和 Y 二者彼此是 independent. d X 和 Y 即为 gross substitutes,亦是 gross complements. 这题答案给: a, b , c 都对， 我的想法; a 跟 b 都对了，那为什麽d就不行呢?? 3. Suppose Charlie Parker CDs cost $10 a piece and Lester Young CDs cost $5 a piece. You have $40 to spend on CDs. The marginial utility that you derive from additional CDs is as follows: Units Consumption Charlie Parker Lester Young 1 60 30 2 40 28 3 30 24 4 20 20 5 10 10 How many of each CD would you buy to maximize your utility? 答案: Parker 2张, Young4张 我的答案是 Parker 3张，Young 2张．明明Young的边际效用没有比 Parker来得大啊??，在所得允许之下不是要先选择边际效用 较大的吗?? --

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