430 1 For a company that manufactures tennis rackets, the average cost per racket is found to be 5 = T + 9 + EX forx 2 1' where x is the number of rackets produced per hour. Use the differential to approximate the change in average cost per racket if production is (A) increased from 25 per hour to 31 per hour and (8) increased from 30 per hour to 36 per hour. t")