4. (15 points) A stone of mass m_A = 23 kg initially slides on a frictionless surface at 2.5 m/s in the positive x-direction. It collides with another stone of mass m_B = 11 kg which is initially at rest. After the collision, stone A is moving at 1.2 m/s in a direction that makes an angle alpha = 33 with respect to the positive x-direction. What is the final velocity of stone B? (Remember to find the magnitude and direction of the velocity.)