Finding Price Elasticity through differentiation

help please...

Suppose the demand function for a particular graphing calculator is

D( p) = 1000 e - 0.02 p

a. Find the price elasticity of demand, the revenue function, and how revenue changes with price (dR/dp).

b. Determine the range of prices for which this demand function is elastic (, > 1) and inelastic (, < 1).

c. Determine how the elasticity of demand is related to the way that revenue responds to price increases (i.e., how does the sign of dR/dp relate to whether the function is elastic or inelastic?).