The Demand for Watches Is Q = 1,000P^-2

The demand for watches is Q = 1,000P^-2.50I². Assume that per capita income I is $6,000. At a price P of $45, the price elasticity of demand is

A) 1.0.
B) 2.25.
C) 2.
D) -0.50.
E) 2.50.