400 1 For a company that manufactures tennis rackets, the average cost per racket is found to be C = X +7+ -x for x 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 10 per hour to 16 per hour and (B) increased from 45 per hour to 51 per hour. .. . (A) If production is increased from 10 per hour to 16 per hour the average cost per racket will increase | by approximately $ per racket