increase prices, reduce production, and realise positive economic profits. Supply curve: in a perfectly competitive market there is a well defined supply function with a one-to-one relationship between price and quantity supplied. In a monopolistic market no such supply relationship exists. A monopolist cannot trace a short-term supply curve because for a given price there is not a unique quantity supplied. As Pindyck and Rubenfeld note, a change in demand "can lead to changes in prices with no change in output, changes in output with no change in price or both". Monopolies produce where marginal revenue equals marginal costs. For a specific demand curve the supply "curve" would be the price-quantity combination at the point where marginal revenue equals marginal cost. If the demand curve