Gains from Trade: A Numerical Example
1. A closed Economy's problem
PPF: y12 + 4 y22 = KL, MRT = y1/4y2.
Utility: U = x1x2, MRS = x2/x1
Constraint: x1 = y1, x2 = y2.

2. An Open Economy's Problem
K = 80, L = 10,
p*1 = p*2 = 1.
Step 1: Choose y1 and y2 to Maximize GDP

Step 2
Choose x1 and x2 to maximize U(x1,x2)
Prices: p*1 = p*2 = 1.
Budget Constraint: p*1x1 + p*2x2 = Io(income from step 1).

Homework 2
Production possibility frontiers, MRT, utility function, MRS,
resource supplies and international prices are as follows:
PPF: y12 + 4 y22 = KL, MRT = y1/4y2.
Utility: U = x1x2, MRS = x2/x1
K = 18, L = 100,
Prices: p*1 = p*2 = 2.
A. The autarky problem:
Find y1, y2, UA, (p1/p2)A in autarky.
B. Optimal production under free trade:
Given international prices, p*1, p*2, find optimal output, y1, y2, and Io (maximized income) evaluated at world prices.
F. Optimal consumption under free trade:
Find, x1, x2, UF, z1 (export) and z2 (import).
G. Evaluate the gains from trade, G = UF - UA.
S. Sketch the solutions and carefully label points A, B, and F.
This concludes the math portion of the course.