Answer
given,
mass of base ball = 0.14 kg
speed before it made the contact with the ball (V i) = 42 m/s
speed after batter hit the ball(V f) = - 48 m/s
a)
impulse = change in momentum
=
=

= -12.6 Kg m/s
Magnitude of impulse = 12.6 Kg m/s
b)
Force =

=

Force = 2520 N