i am not sure how to start the problem. please circle answer and show all calculations

A. (15 points) A 0.140-kg baseball is dropped from rest from a height of 2.2 m above the ground. It rebounds to a height of 1.6 m. What change in the ball's momentum occurs when the ball hits the ground? B. (15 points) A 920-g piece of iron at 100"C is dropped into a calorimeter of negligible heat capacity containing 50 g of ice at 0"C and 92 g of water, also at 0"C. What is the final temperature of the system? The specific heat of iron is 448 J/(kg K) and the latent heat of fusion of water is 33.5 x 10* J/kg