his chapter discusses many types of costs: explicit costs, implicit costs, total cost, average fixed cost, average variable cost, and marginal cost. Fill in the type of cost that best completes each sentence. Profits equal total revenue minus . The term refers to costs that involve direct monetary payment by the firm. is falling when marginal cost is below it and rising when marginal cost is above it. The cost of producing an extra unit of output is the . is always falling as the quantity of output increases. The opportunity cost of running a business that does not involve cash outflow is