Olaf is standing on a sheet of ice, there is a negligible friction between his feet and the ice. A friend throws Olaf a ball that is horizontally traveling toward Olaf. The mass of ball is 0.50kg and the mass of Olaf's is 80kg. When Olaf catches the ball, he throws the ball back to his friend with the same speed but opposite direction. After the ball leaves his hand, Olaf moves backward with speed of 0.30 m/s. What is the speed of the ball?( Draw a motion map of the system you choose and define the positive direction)