Find the speed and direction of a particle which, when projected from a point 15m above the horizontal ground, just clears the top of a wall 26¼m high and 30m away.

sol: 25m/s and 36°52'

I have been at this for a while and cannot figure it. Not sure if I can assume that the maximum height is 26¼m or not, and even so, still can't figure out the equations and how to solve with 3 unknowns and only 2 equations

my starting point is this so far:

x = vt cos a and y = vt sin a - 4.9t² + 15

thanks

jacs