An accessories company finds that the cost, in dollars, of producing x belts is given by C(x) = 720+30x-0.064x. Find the rate at which average

An accessories company finds that the cost, in dollars, of producing x belts is given by C(x) = 720+30x-0.064x². Find the rate at which average cost is changing when 172 belts have been produced.First, find the rate at which the average cost is changing when x belts have been produced.c=0When 172 belts have been produced, the average cost is changing at for each additional belt.(Round to four decimal places as needed)