Consider the comparative statics of the farmer's fencing problem in Learning-By-Doing Exercise 1.4, where L is the length of the pen, W is the width, and A = LW is the area.
a) Suppose the number of feet of fence given to the farmer was initially F1 = 200. Complete the following table. Verify that the optimal design of the fence (the one yielding the largest area with a perimeter of 200 feet) would be a square.

b) Now suppose the farmer is instead given 240 feet of fence (F2 = 240). Complete the following table. By how much would the length L of the optimally designed pen increase?

c) When the amount of fence is increased from 200 to 240 (ΔF = 40), what is the change in the optimal length (ΔL)?
d) When the amount of fence is increased from 200 to 240 (ΔF = 40), what is the change in the optimal area (ΔA)? Is the area A endogenous or exogenous in this example? Explain.

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