The demand for a particular commodity is given by D(x) = -35x + 200; that is, x units will be demanded at a price of p = D(x) dollars per unit.

Consumer expenditure E(x) is the total amount of money consumers pay to buy x units.Consumer Expenditure E as a function of x is expressed as:

E(x) = x * D(x)

where

x(-35x+200)

simplified as

-35x^2 + 200x

Find the average rate of change in consumer expenditure as x changes from x = 4 to x = 5.