Answer

a) Change in momentum = 0.080 kg x 32 m s^-1 - 0.080 kg x -22 m s^-1 (1) = 4.32 kg m s^-1 (1)

b) F = Δp / t (1) = 4.32 kg m s-1 / 0.15 s (1) = 28.8 N (1)

c) Momentum is conserved (1). The wall and the Earth gain equal momentum in the opposite direction (1)