A major difference between monopoly and perfect competition is that... a. Monopolistic firms tend to maximise revenue while perfectly competitive firms maximise profit. b. Monopolists do not consider consumer demand when choosing price and output levels. O c. Perfectly competitive firms cannot maintain positive economic profits in the long run, whereas monopolists can. d. Perfectly competitive firms can never earn economic profits; monopolistic firms always earn economic profits. O e. Monopolistic firms emphasise cost minimisation whereas perfectly competitive firms emphasise profit maximisation