8x-9 The total cost (in hundreds of dollars) to produce x units of perfume is C(x)= 7x+8 (a) Find the average cost function. (b) Find the marginal average cost function. (c) Find the average cost and the marginal average cost for a production level of 20 units. Interpret your results. (a) The average cost function is C(x)= (b) The marginal average cost function is C'(x)=- (c) The average cost for 20 units is $ per unit. The marginal average cost for 20 units is $ . (Round to the nearest cent as needed.) Interpret your results. When 20 units are produced, the average cost is $ per unit and the average cost is $per unit. (Round to the nearest cent as needed.) at a rate of about