how do you solve this

L011-2 9. Suppose that the following schedule summarizes the sales (demand) situation confronting an oligopolist: Price (per unit) $8 $10 $12 $14 $16 $17 $18 $19 $20 Quantity demanded (units per period) 10 7 6 2 Using the following graph, (a) Draw the demand and marginal revenue curves facing the firm. (b) Identify the profit-maximizing rate of output in a situation where marginal cost is constant at $11 per unit. $20 19 18 17 16 15 PRICE OR COST (dollars per unit) A 2 3 4 5 6 8 9 QUANTITY (units per period) 262