calculations of average forces?

Question

A 0.145 kg baseball pitched at 36.0 m/s is hit on a horizontal line drive straight back toward the pitcher at 52.0 m/s. If the contact time between bat and ball is 3.00 10-3 s, calculate the average force between the ball and bat during contact

Answer 1

force=d(mv)/dt so
average force = m(v1-v2)/t = .145x88/.003