Two identical balls `A` and `B` lie on a smooth horizontal surface, which gradually merges into a curve to a height `3.2 m`. Ball `A` is given a velocity of `10 m//s`, to collide head-on with ball `B`, which then takes up the curved path. What is the minimum coefficient of restitution, `e`, for the collision between `A` and `B` in order that ball `B` reaches the highest point `C` of the curve.