The US had a surplus on its current account in 2009

A monopolist will operate where

a. MR = MC and charge a price equal to marginal revenue. b. MR = MC and charge a price equal to marginal cost. c. MR = MC and charge a price corresponding to demand at that level. d. MC = MR and charge a price corresponding to average cost.

If all existing firms and all potential firms have the same cost curves, there are no inputs in limited quantities, and the market is characterized by free entry and exit, then the long-run market supply curve

a. is horizontal and equal to the minimum of long-run marginal cost for each firm. b. must slope downward. c. must slope upward. d. is horizontal and equal to the minimum of long-run average cost for each firm.