Consider the following demand and supply relationships in the market for golf balls: Q^d= 90 − 2P − 2T and Q^s= −9 + 5P − 2.5R, where T is the price of titanium, a metal used to make golf clubs, and R is the price of rubber.

a) If R = 2 and T = 10, calculate the equilibrium price and quantity of golf balls.

b) At the equilibrium values, calculate the price elasticity of demand and the price elasticity of supply.

a는

90-2P-20 = -9+5P-5

70-2P = -14+5P

84 = 7P

P = 12

Q = 90-24-20 = 46

b는 

수요의 가격 탄력성 : -2 * 12 / 46 = - 0.52

그렇다면 공급의 가격 탄력성은 어떻게 구하죠????