The Demand for Watches Is Q = 1,000P^-0

The demand for watches is Q = 1,000P^-0.50I^-1. Assume that per capita income I is $5,000. At a price P of $50, the price elasticity of demand is

A) 2.50.
B) 1.0.
C) -1.
D) -1.50.
E) 0.50.