If peanut butter and jelly are complements, then their cross elasticity of demand must be

The MFC curve increases for a monopsonist because:

a. hiring more workers raises total labor costs. b. output price rises as a firm's market power increases. c. hiring more workers does not affect wages. d. the later workers hired are less productive. e. as more workers are hired, all workers receive higher wages.

In building economic models, economists often omit

a. assumptions. b. theories. c. details. d. equations.