Initial velocity not given

[SOLVED] Initial velocity not given

Hello,
I was looking for a strategy for finding the initial velocity for a problem that gives the angle and height. The problem is: A ball is dropped and rebounds with an intial velocity of what magnitude considering the ball must bounce through an opening that is between 3.1-4.9 feet high.

I tried some manipulation but couldnt get the correct answer....which is around 15-20 ft/s

Thanks