A hockey ball of mass `200g` travelling from west to east at `10m//s` is struck by a hockey stick. As a result, the ball gets turned back and now has a speed of `5m//s`. If the ball and hockey stick were in contact for `0.2s`, Calculate
(i) initial and final momentum of the ball
(ii) rate of change of momentum of the balll
(iii) force exerted by hockey stick on the ball.