Suppose that you are on the board of directors for an oil firm which is the dominant firm in the industry( thus it lets all the other firms in the industry sell whatever they want). Thus the other small firms acts as perfect competition however you decide on the price and the other firms accepts. The demand curve for the industry Q= 300-P or P =300-Q. The total output supplied by little firms (Qr) is given by the Qr=49p. If your firms production is Qb and if the Marginal cost curve for your firm is given by MCb= 2.96 Qb