There are many industries. Economist group them into four market models: 1) pure competition which involves a very large number of firms producing a standardized producer. New firms may enter very easily. 2) Pure monopoly is a market structure in which one firm is the sole seller a product or service like a local electric company. Entry of additional firms is blocked so that one firm is the industry. 3)Monopolistic competition is characterized by a relatively large number of sellers producing differentiated product. 4)Oligopoly involves only a few sellers; this “fewness” means that each firm is affected by the decisions of rival and must take these decisions into account in determining its own price and output. Pure competition assumes that firms and resources are mobile among different kinds of industries.
No single firm can influence market price in a competitive industry; therefore a firm’s demand curve is perfectly elastic and price equals marginal revenue. Short-run profit maximization by a competitive firm can be analyzed by comparing total revenue and total cost or applying marginal analysis. A firm maximizes its short-run profit by producing that output at which total revenue exceeds total cost by the greatest amount.
A complete firm maximizes profit or minimizes loss in the short run by producing that output at which price or marginal revenue equals marginal cost, provided price exceeds minimum average variable cost. If price is less than average variable cost, the firm minimizes its loss by shutting down. If price is greater than average variable cost but less than average cost, the firm minimizes its loss by producing the P=MC output. The firm minimizes its economic profit at P=MC output if price exceeds average total cost.
Applying that MR(=P)=MC...