Which of the following groups would have the lowest unemployment rates?

If firms in a competitive market have different cost functions, then

A) there is no short run market supply curve. B) the market supply curve reflects those firms' operating envelopes, even in the short run. C) some of the firms will shut down because their costs are too high to compete. D) the firms' marginal costs will be different at the market price.

In competitive markets, the elasticity of labor supply is:

a. unrelated to time. b. inversely proportional to time elapsed since a wage change. c. unity. d. directly proportional to time elapsed since a wage change.