An accessories company finds that the cost, in dollars, of producing x belts is given by C(x) = 740 + 34x - 0.063x^2. Find the rate at which average cost is changing when 171 belts have been produced.
First, find the rate at which the average cost is changing when x belts have been produced.
C'(x) =
When 171 belts have been produced, the average cost is changing at for each additional belt.
(Round to four decimal places as needed.)