Two spheres of masses 1.0 kg and 1.5 kg hang at rest from two strings 1.5 m long (one string per sphere). Both strings are attached to the same hook on the ceiling. The lighter sphere is pulled aside until its string makes a 60 degree angle with the vertical. It is let go and it collides elastically with the heavier sphere. After they rebound, what is the largest angle with respect to the vertical that the string holding the lighter sphere will make?