Prices under different market structures. How are prices determined under perfect competition? Think about a firm that you have done business with recently. To what industry does this firm belong? For example, McDonald's is a firm in the fast food industry. What market structure would this industry fall under? What are the names of other firms in this industry? Is it monopolistic competition, oligopoly, monopoly, or perfect competition? How does market structure affect the firm's ability to set the price for its products?