The Inverse Demand Function for Grapes Is Described by the Equation

The inverse demand function for grapes is described by the equation p = 676 - 9q, where p is the price in dollars per crate and q is the number of crates of grapes demanded per week. When p = $28 per crate, what is the price elasticity of demand for grapes?

A) -9/676
B) -9/72
C) -72/28
D) -252/72
E) -28/648