A ball is thrown straight up from the ground with speed vsub0. At the same instant, a second ball is dropped from rest from a height H, directly above the point where the first ball was thrown upward. There is no air resistance. A) Find the time at which the two balls collide. B) Find the value of H in terms of vsub0 and g so that at the instant the balls collide, the first ball is at the highest point of its motion.