According to Pindyck and Rubinfeld the estimated demand and supply functions for wheat in the United States in 1981 were:

QWD = 3,550 - 266 P_W,

QWS = 1,800 + 240 P_W,

Where, P is the farm price of wheat (in dollars per bushel)

QWDis the quantity demanded of wheat (in millions of bushels), and

QWS is the quantity supplied of wheat (in millions of bushels)

Calculate the price elasticity of demand for wheat at the equilibrium price.

a. -0.45.

b. -0.35.

c. -0.39.

d. -0.42.

e. None of the above