consider the velocity of the ball towards the wall as negative and away from the wall as positive.
m = mass of the ball = 513 g = 0.513 kg
v₀ = initial velocity of the ball towards the wall before collision = - 14.7 m/s
v = final velocity of the ball away from the wall after collision = 11.3 m/s
t = time of contact with the wall = 0.038 sec
F = average force acting on the ball
using impulse-change in momentum equation , average force is given as
F = m (v - v₀)/t
inserting the values
F = (0.513) (11.3 - (- 14.7))/0.038
F = 351 N