4.12 By studying, Will can produce a higher grade, GW, on an upcoming economics exam. His production function depends on the number of hours he studies marginal analysis problems, A, and the number of hours he studies supply-and-demand problems, R. Specifically, GW = 2.5A0.36R0.64. His roommate David’s grade-production function is GD = 2.5A0.25R0.75.

a. What is Will’s marginal product of studying supply-and-demand problems? What is David’s?

(Hint: See Appendix 6C.)

b. What is Will’s marginal rate of technical substitution between studying the two types of problems?

What is David’s?

c. Is it possible that Will and David have different marginal productivity functions but the same marginal rate of technical substitution functions? Explain. (Hint: See the section

“Cobb-Douglas Production Function.”)