With what speed do olaf and the ball move afterward

Solve the all parts of following question given below:

Question: Olaf is standing on a sheet of ice that covers the football stadium parking lot in Buffalo, New York; there is negligible friction between his feet and the ice. A friend throws Olaf a ball of mass 0.400kg that is traveling horizontally at 10.9m/s . Olaf's mass is 72.0kg.

Part A: If Olaf catches the ball, with what speed vf do Olaf and the ball move afterward?

Part B: If the ball hits Olaf and bounces off his chest horizontally at 8.00m/s in the opposite direction, what is his speed vf after the collision?

I'm having problems with this question. Please, show me the process of solution. Thanks!