EC1109 Mathematics for Economics Spring 2022 Problem Set #3
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EC1109
Mathematics for Economics
Spring 2022
Problem Set #3
1. (a) Find optimal activity levels and equilibrium prices for the following linear programming problem:
max 2x1 + 4x2
s.t. x1 + 2x2 # 8 (K)
x1 + x2 # 5 (N)
3x1 + 8x2 # 30 (L)
x1 , x2 $ 0.
(b) Calculate how much the maximal level ofoutput increases when the endowment ofK increases. Make the same calculation when N increases. Compare these marginal products with the prices you found in part (a). What is going wrong?
2. Solve the following two minimization problems using the Lagrange multiplier-equilibrium method:
min 5x1 + x2
s.t. 4x1 + 6x2 $ 14
x1 + x2 $ 3
x1 $ 0, x2 $ 0.
min 9x1 + 14x2 + 8x3
s.t. 2x1 + 2x2 + 5x3 $ 14
2x1 + 4x2 + x3 $ 10
x1 $ 0, x2 $ 0, x3 $ 0.
3. Find an equilibrium and solution for each of the following problems that uses prices for the nonnegativity constraints.
(a)
(b)
max 4x1 + 2x2 s.t. 2x1 + 3x2 3x1 + x2 x1 , x2 |
# 8 # 14 $ 0. |
max 2x1 + 5x2 + 7x3
s.t. 4x1 + 2x2 + x3 #
2x1 + x2 + 5x3 # x1 , x2 , x3 $ 0.
(K) (N)
9
18
(K)
(N)
2 2
4. Consider the functionf, defined on all (x1 , x2) $ 0, given byf (x1 , x2) = x13 x23 .
M2f (x1,x2) (a) Calculate the second partial derivatives
always positive or negative. Mx
and
to see if they are Mx
(b) Isf concave? (Hint: apply the chord definition of concavity to two points in the domain off, say x = (0, 0) and y = (2, 2), and set α equal to a value, say 1'2, wheref (x),f (y), and f (αx + (1 ! α)y) are all easy to calculate.)
2022-01-27