课程名称︰个体经济学 课程性质︰必修 课程教师︰江淳芳 开课学院：社会科学院 开课系所︰经济学系 考试日期（年月日）︰101年11月08日 考试时限（分钟）：210分 是否需发放奖励金：是 （如未明确表示，则不予发放） 试题 : Short Questions (20%) 1.(8 points)David consumes only cookies and books. At his current consumption bundle, his marginal utility from books (MUbook) is 10 and his marginal utility from cookies(MUcookie) is 5. Each book costs $10, and each cookie costs $2. Is he maximizing his utility? Explain. If he is not, how can he increase his utility while keeping his total expenditure constant? 2.(12 points) Please write a brief but convincing explanation fo your answers. (a) If James spend his entire income, is it possible for all goods he buys to be normal? Explain. (b) If James spend his entire income, is it possible for all goods he buys to be inferior? Explain. (c) If James spend his entire income, is it possible for the income elasticity of demand for every good to be bigger than 1? Explain. Long Questions(80%) 1.(10 points) Ginger's utility function is U(x,y)=x^y. She has income I=240 and faces prices Px=$8 and Py=$2. (a) Determine Ginger's optimal basket given these prices and her income. (b) If the price of y increases to $8 and Ginger's income is unchanged, what must the price of x fall to in order for her to be exactly as well off as before the change in Py? 2.(20 points)Suppose an individual's utility funtion is given by U(x,y)=x^(1/3) *(y-6)^(2/3),where we interpret 6 as the minimum quantity of good y that the individual must consume to remain alive an well. Let Px be the price of good x and Py be the price of good y. Assume that the income of this individual (denoted I) is strictly larger than 6Py. (a) Compute the marginal utility of x and the marginal utility of y.(4 points) (b) Compute the marginal rate of substitution. (2 points) (c) Derive the demand for good x and the demand for good y as functions of the two prices, Px and Py, and income. (4 points) (d) Derive the change in the quantity demanded of good x in response to a change in the price of good y. Is good y a complement or a substitute (or neither) for good x?Explain your answer. (4 points) 3.(25 points) Hal's utility from food, denominated in dollars, can be represented by the utility function U(x,m)=2X^(1/2)+m, where x is the quantity of food he consumes and m is his expenditure on all other goods. You can now think of Hal as consuming two goods---food(x) and money(m). Suppose the price of food is Px per unit and that Hal's total income is $M. The "price" of money under this interpretation of the model is Pm=1; each additional unit of m he consume costs $1. (a) What is Hal's demand for food when the price of food is Px=$0.5?(7 points) (b) How does Hal's demand for food change (increase, decrease, or neither) when his income increases? (Px remain $0.5)(5 points) (c) Supose the income $M is $10, how many units of food does he consume? (Px remains $0.5) (3 points) (d) Following (c), suppose now the price of x drrops to $0.20, what are the slutsky substitution effect and income effect on the consumption of x from the decline in the price of food? (10 points) 4.(25 points) Suppose that all concumers have identical preferences over gasoline (x) and expenditure on all other goods (y). The price of gasoline is p. Each consumer has income m. So the budget constraint can be expressed as p*x+y=m. Please consider the following two tax plans: Plan A (tax rebate based on final consumption): The government raises the price of gasoline from p to p+t. And the government also gives all tax revenue back to consumers. That is, when a consumers consumes x' gasoline after the price change, the government will give t*x' to the consumer. Plan B (tax rebate based on initial consumption): The government raises the price of gasoline from p to p+t. And the government will give the consumer t*x. (x is the initial consumption amount of gasoline). (a) Would the consumer be better off or worse off is Plan A were in effect? Explain.(10 points) (b) If Plan B were in effect, would the consumer consume more or less gasoline than the initial consumption of gasoline? Explain.(7 points) (c) Would the consumer be better off or worse off is Plan B were in effect? Explain. (8 points) --

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