Problem: An inflatable raft (unoccupied) floats down a river at an approximately constant speed of 3.7 m/s. A child on a bridge, 62 m above the river, sees the raft in the river below and attempts to drop a small stone onto the raft. The child releases the stone from rest.

A- In order for the stone to hit the raft what must be the horizontal distance between the raft and the bridge when the child releases the stone?

I've been having quite a bit of trouble understanding this problem, Thank You so much for your help. Thank you.