Dominant Firm with a Competitive Fringe Suppose that the market demand for oranges is Q = 1000 − 2P , where Q = n ∗ Qf + Qd and Q is the total quantity, Qf is the quantity supplied by a single competitive fringe ?rm and Qd is the quantity supply by the dominant ?rms. The dominant ?rm’s marginal cost is given by mcd = 100, QD and the competitive fringe’s supply curve is given by Qf = −120 + P . There are three competitive fringe ?rms in the market.