For a company that manufactures tenns rackets, the average cost per racket is found to be C=x400+7+21 for 1, where is the number ot rackets produced per hout Use the difterential to approwmate the change in average cost per racket if proouction ia (A) incroased from 15 per hour to 18 per nour and (B) incieased ticm 45 per heur to 4 ber hour (A) If productoon is increased from 15 per hour to 18 per hour the average cost per tacket wil by approximateys pertacket (B) If pioguction is increased from 45 per hour to 48 per hour the average cost per racket we by apgrcoimatelys per racket