Let:
m- 0.0600Kg
v1- +50.0 m/s
v2- -42 m/s
a)
momentum1 - momentum2 = impulse
p1 - p2 = Ft
m(v1 + v2) = Ft
Ft = 0.54 N-s
b)
Work is traditionally force times distance but an easy way to get through this one is to think logically and keep your units straight:
The racket creates an overall velocity of 90 m/s for the ball:
W=(Ft)(V)
W=0.54 N-s 90 m/s
W=48.6 N-m = 48.6 J