Suppose that the dollar cost of producing x appliances is c(x) = 800 + 70x-0.4x². a. Find the average cost per appliance of producing the first 80 appliances. b. Find the marginal cost when 80 appliances are produced. c. Show that the marginal cost when 80 appliances are produced is approximately the cost of producing one more appliance after the first 80 have been made, by calculating the latter cost directly. The average cost per appliance of producing the first 80 appliances is $ ☐ /appliance. (Round to the nearest cent as needed.) The marginal cost when 80 appliances are produced is $ (Round to the nearest cent as needed.) The cost of producing one more appliance beyond 80 appliances is $ (Round to the nearest cent as needed.)