4. The total cost, in dollars, of producing x units of a certain product is given by

C (x) = 8x + 20 + x3

100

and the average cost is defined by A(x) = C(x)/x.

(a) Find A0(x) and C0(x).

(b) Find the minimum of A(x) and the value x0 at which it occurs.

(c) Compare A(x0) and C0(x0).