20. Which of the following is unique to a monopolistically competitive firm when compared to an oligopoly a. Monopolistic competition features many buyers b. The monopolistically competitive firm advertises. istically competitive firm produces a quantity of output that falls short of the socilly optimal level. d. Monopolistic competition features many sellers. 21. Which of these types of costs can be ignored when an individual or a firm is making decisions? a. sunk costs b. variable costs c. opportunity costs d. marginal costs 22. Consider a competitive market with a large number of identical firms. In long-run equilibrium, market price is a. a firm's level of sunk costs. b. the minimum point on the firms' average total cost curve. c. the minimum point on the firms' average variable cost curve d. the portion of the marginal cost curve below average variable cost