Suppose total cost in dollars from the production of x printers is given by C(x) = 0.0001x^3 + 0.005x^2 + 28x + 3000
(a) Find the average rate of change of total cost when production changes from 300 to 600 printers.
(b) Find the average rate of change of total cost when production changes from 600 to 700 printers.