课程名称︰个体经济学 课程性质︰必修 课程教师︰黄景沂 开课学院：社会科学院 开课系所︰经济学系 考试日期（年月日）︰100/11/14 考试时限（分钟）：180分钟 是否需发放奖励金：是 （如未明确表示，则不予发放） 试题 : You have to provide explanations for all of your answers. 1. Anne's utility on milk (X) and juice (Y) can be expressed as u(x,y) = √x ＋ 2 √y. (a) (5%) Suppose that Anne spends I dollars on milk and juice every month. The price of milk is Px, and the price of juice is Py. How much milk does she consume in a month? (express your answer as a function of Px, Py,and I) (b) (5%) Suppose that Px=1, Py=1 and I=10. Use your answer in part (a) to compute Anne's price elasticity of demand for milk. (c) (5%) Suppose that Px=1, Py=1 and I=10. Use your answer in part (a) to compute Anne's income elasticity of demand for milk. (d) (5%) Suppose that Px=1, Py=1 and I=10. Use your answer in part (a) to compute Anne's cross elasticity of demand for milk. Are milk and juice substitutes or complements for Anne? 2. Bruce's utility on milk (X) and juice (Y) can be expressed as u(x,y)= x+y. Suppose that Bruce spends 1000 dollars on milk and juice every month. The price of milk increases from $15 to $25. However, the price of juice is fixed at $20. (a) (10%) How much milk does he consume in a month before the price increase? How much milk does he consume in a month after the price increase? (b) (10%) How much of the change in his milk consumption is due to the substitution effect? How much of the change in his milk consumption is due to the income effect? (Please use Hicks' definition to decompose the effects.) 3. (10%) Consider th following two policiees: (a) giving everyone a NT$3,600 consumption voucher (消费券) ; (b) reducing tax rate on everyone's wage income by 10%. Suppose you have well-behaved preference with strict convexity, and you like these two policies equally. Will policy (b) reduces your tax payment by more than NT$3,600 or less than NT$3,600? 4. (15%) We say that a consumer has a well-behaved preferences if his/her preference is complete, transitive, monotonic, and convex. We observe the consumption behaviors of Cindy, David, and Eddy in two different months: September and October. Suppose they only consume two goods X and Y. Their tastes do not change in these two months, but the prices of X and Y differ over time. Can you tell who does not have a well-behaved preference? Explain your answer. --------------------------------------------------------------------- September October --------------------------------------------------------------------- Price (Px,Py) (2,3) (3,4) --------------------------------------------------------------------- Cindy's choice (Xa,Ya) (10,19) (35,5) David's choice (Xb,Yb) (25,15) (10,26) Eddy's choice (Xc,Yc) (11,20) (25,10) ===================================================================== 5. (15%) Coffee currently sells for $50 per cup. Suppose that the government simultaneously institutes an excise tax of $10 per cup and a sales subsidy of $10 per cup. (The "sales subsidy" means that every time you buy a cup of coffee, you get $10 from the government.) What is the new market price of coffee? Are demanders helped or hurt by this pair of policies? What about suppliers? 6. (10%) Why is the substitution effect always negative for a consumer with well-behaved preference when the price of a produce increases? 7. Suppose the amount of time required for Fay and Grace to bake one unit of cake or pizza is given by the following table: ------------------------------- cake pizza ------------------------------- Fay 5 hours 6 hours Grace 3 hours 4 hours =============================== If an individual bakes x units of these foods, the required time is x multiplies the values given in the above table. For simplicity, we will allow x to be a non-integer mumber. (a) (5%) Who has the comparative advantage at cake? At pizza? (b) (5%) Suppose the two persons can trade. The exchange rate for one unit of cake is x units of pizza. Find out all possible values of x such that both persons can benefit from trade. --

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