Answer:
The magnitude of the average acceleration of the ball during the contact with the bat is 90666m/s^2
Step-by-step explanation:
Average acceleration (a) is defined as the change in velocity divided by the time it took:
(eq. 1)
V2: final velocity
V1: initial velocity
t: time the change in velocity took
In this example, the ball traveled at 96mi/h in a direction and changed its velocity to 56mi/h in the opposite direction because of the contact with the bat.
In this case, we need to express all in meters and seconds. To achieve this use some conversion factors:

Note there's a negative sign beside 56 mi/hr because it goes in the opposite direction to 96 mi/hr.
Plugging in these values in eq. 1:
