Two-part tariff (25 points) Consider the following simple two-part tariff problem. There are two consumers. The first consumer's demand curve is and the second consumer's demand curve is . The marginal cost is .

a). (10 points) If the firm wants to charge the fixed fee that is equal to one consumer's surplus, how should he sets the two-part tariff T and P, where P is the price?

b). (15 points) Now firm want to set an optimal two-part tariff. Write out the firm's profit function and solve optimal T and P.