EC2210 Mathematical Economics 1B Summer Examinations 2020/21
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EC2210
Summer Examinations 2020/21
Mathematical Economics 1B
1. Consider the following preference relation 5 defined on R : |
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if min {xl , x2 } > min {yl , y2 } and min {xl , x2 } > 0 if min {xl , x2 } = min {yl , y2 } = 0 and x (0, 0) and y (0, 0) if min {yl , y2 } = 0 |
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(a) Are these preferences rational? (15 marks) |
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(b) Are these preferences monotone? (10 marks) |
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(c) Are these preferences strongly monotone? (10 marks) |
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(d) Are these preferences continuous? (15 marks) |
2. Consider a two-commodity, two-consumer exchange economy, in which the consumption set
of each consumer is R . Let xij denote the consumption by agent i e {1, 2} of commodity
j e {1 , 2} and let xi = (xil , xi2) denote i’s consumption bundle. Consumer 1 ’s preferences
can be represented by the utility function:
ul (xll , xl2 ) = xll(2) + xl2(2)
Consumer 2’s preferences can be represented by the utility function:
u2 (x2l , x22 ) = xlx2
Let ωi e R be the endowment of consumer i. Suppose ω l = (a, 0) and ω2 = (0, b) where
a > 0 and b > 0 . You can use graphs to answer this question but please make sure you
explain them very carefully.
(a) Are the preferences of these consumers convex? Justify your answer. (10 marks) (b) Derive the Walrasian demand correspondence for consumer 1. (15 marks)
(c) Derive the Walrasian demand correspondence for consumer 2. (15 marks)
(d) For what values of a and b does a Walrasian equilibrium exist? (10 marks)
3. Consider a two-commodity, two-consumer production economy with one firm. Commodity 1 is leisure while commodity 2 is produced by a perfectly competitive firm endowed with production function f (K, L) given by:
f (K, L) = K8 Ll一8 for (K, L) e R
where K and L are the amounts of capital and labour used to produce commodity 2, respectively. Let l¯i , i and θ¯i be individual i′ s endowments of leisure, capital and shares of the firm, respectively. Consumer 1, called the worker, is endowed with ╱l¯l , l , θ¯l ← = (1, 0, 0) and has a utility function ul (xll , xl2 ) = xll(a)xl(l)2(一)a for all (xll , xl2 ) e R . Consumer 2, called the capitalist, is endowed with (l¯2 , 2 , θ¯2 ) = (0, 1, 1) and has a a utility function
u2 (x2l , x22 ) = x22 for all (x2l , x22 ) e R . Let p, w and r denote the output price, the wage
and the cost of capital, respectively.
(a) Define a Walrasian equilibrium with production for this economy. (10 marks)
(b) Show that the cost function of the firm is C(w, r, y) =╱←8 ╱ l 一(叫)8 ← l一8 y where y is the output of commodity 2. Find the supply correspondence y(p, w, r). (10 marks)
(c) Show that in any Walrasian equilibrium p = ╱ ←8 ╱ l 一(叫)8 ← l一8 > 0. (15 marks)
(d) Find a Walrasian equilibrium for this economy and explain how the income shares of the worker and the capitalist change when β increases. What is the economic intuition?
(15 marks)
2022-06-02