9. Suppose that the demand for a concert, QD, is represented by the following equation, where P is the price of concert tickets and Q is the number of tickets sold: QD = 2500 - 20P The supply of tickets, QS, is represented by the equation QS = -500 + 80P

a. Find the equilibrium price and quantity of tickets sold. (Hint: Set QD = QS and solve for the price, P, and then plug the result back into either of the original equations to find QE.)

b. Carefully graph your result from part a.

c. Calculate the consumer surplus at the equilibrium price and quantity. (Hint: Because the area of consumer surplus is a triangle, you will need to use the formula for the area of a triangle, 12 * base * height, to solve the problem.)