4–26. OPEC is a cartel of oil producing countries that attempts to use its market power to control oil prices. Assume the current daily demand for OPEC’s oil is given by the following equation:

P = 50 − 0.001Q where P is the price per barrel (ppb) and Q is the quantity of barrels sold daily (in thousands). Moreover, suppose the marginal cost of producing a barrel is constant at zero.