consider the initial direction of motion of ball before being hit by the bat as negative direction and direction of motion after being hit by bat as positive direction of motion .
v₀ = initial velocity of ball before being hit by the bat = - 37.9 m/s
v = final velocity of ball before being hit by the bat = 20 m/s
m = mass of the ball = 0.17 kg
t = time of contact = 90.5 ms = 0.0905 sec (since 1 milli = 0.001)
F = size of net force
using impulse - change in momentum equation
F t = m (v - v₀)
F (0.0905) = (0.17) (20 - (- 37.9))
F = 108.8 N
