A 20 lb sphere A is held at a 60 degree angle shown and is released. It strikes the 10lb sphere B. The coefficient of restitution for this collision is e=0.75. Sphere B is attached to the end of a light rod(neglect the mass) that pivots freely about point O. If the spring constant k=100lb/ft is initially unstretched, determine the maximum rotation of the light rod after impact.