Question 4: a) Illustrate the model of a perfectly competitive firm that is earning economic profits in the short-run. Make sure that you label your graph appropriately. Your graph should have the demand curve facing the firm (do), Price (P.), MR (MR.), MC (MC), and ATC. Identify the optimal level of output (qo), as well as the profit the firm is earning (an area). (4 points) b) Illustrate the model of a perfectly competitive firm that is in long-run equilibrium. Your graph should have the demand curve facing the firm (do), Price (Po), MR (MR.), MC (MC), and ATC (ATC). Identify the optimal level of output (qo). (2 points) What is the firm's profit in the Long-run? (2 points)