A ball of mass moving with velocity strikes a vertical wall. The angle between the ball's initial velocity vector and the wall is as shown on the diagram, which depicts the situation as seen from above. The duration of the collision between the ball and the wall is , and this collision is completely elastic. Friction is negligible, so the ball does not start spinning. In this idealized collision, the force exerted on the ball by the wall is parallel to the xaxis. What is the magnitude of the average force exerted on the ball by the wall?