V3

y =F(21, x2) units of a certain product are produced using two inputs at levels r, and r2 respectively. If wi, w2 and p are the input and output prices, the optimal choice of input demand for input i must necessarily rise if a. F is differentiable. b. Profit displays increasing differences with respect to (p, r;) for each i = 1, 2. c. F is concave. d. F displays increasing differences in the two inputs