Refer to Figure 8.1. At the profit-maximizing level of output, ATC is

Suppose you were to believe that "money illusion" exists that is as prices and incomes both rise proportionally, people buy more. Which of the following characteristics of demand does that cause you to doubt?

a. demand functions are downward sloping b. demand has a positive vertical intercept c. demand has a positive horizontal intercept. d. demand functions are homogeneous of degree zero.

If we sum all the firms' MC curves above their ATC curves, we would derive the perfectly competitive

a. long run cost curve b. short run cost curve c. horizontal cost curves d. short-run market supply curve e. long-run market supply curve