1. This chapter discusses many types of costs: opportunity cost, total cost, fixed cost, variable cost, average total cost, and marginal cost. Fill in the type of cost that best completes the phrases below:

a. The true cost of taking some action is its _______.

b. _______ is falling when marginal cost is below it, and rising when marginal cost is above it.

c. A cost that does not depend on the quantity produced is a _______.

d. In the ice-cream industry in the short run, _______ includes the cost of cream and sugar, but not the cost of the factory.

e. Profits equal total revenue less _______.

f. The cost of producing an extra unit of output is _______.