Answer
The average force exerted on the ball by the bat is $-11622N$
Work Step by Step
According to the impulse-momentum theorem, $$\sum \overline F\Delta t=mv_f-mv_0$$
Here, we neglect the weight of the ball, so the only force exerted on the ball is from the bat, or $\sum \overline F=\overline F_{bat}$
We have $\Delta t=1.1ms=1.1\times10^{-3}s$, $v_0=+40.2m/s$, $v_f=-45.6m/s$ and $m=149g=0.149kg$. So, $$\overline F_{bat}=\frac{mv_f-mv_0}{\Delta t}=-11622N$$
