Answer:
11.47 m high
Step-by-step explanation:
All of the Kinetic Energy converts to Potential energy
1/2 m v^2 = mgh divide both sides by 'm'
1/2 v^2 = gh (note that the masses given are irrelevant !)
(1/2 v^2) / g = h
(1/2 (15^2) / 9.81 = h = 11.47 m