A graph of Price, P, versus Quantity, Q, shows a straight line, M R, decreasing linearly from (0, 100) to (50, 0), a second straight line, Demand, decreasing linearly from (0, 100) to (100, 0), a third straight line, M C, increasing linearly from the origin to (30, 90), and a curved line, A T C, decreasing from (10, 100) and then increasing to (50, 90). At Q = 20, M R = M C at $60, A T C is $70, and the point on the demand curve is $80. At Q = 25, M C = Demand at $75. At Q = 40, the point on the demand curve is at $60.