The average cost per hour in dollars of producing x riding l

The average cost per hour in dollars of producing x riding lawn mowers is given by the following.

C(x)=0.2x2+20x242+ 2200/x

(a) Use a graphing utility to determine the number of riding lawn mowers to produce in order to minimize average cost.

(b) What is the minimum average cost?

C(x) = 0.2x² + 20x 242 + 2200/x

Take the derivative.
C\'(x) = 0.4x + 20 - 2200/x^2
Set that equal to 0 and solve for x.
0.4x + 20 - 2200/x^2 = 0

0.4*x^3 + 20x^2 - 2200 = 0
There\'s a real solution = 9.6

C(9.6) = $197.6