Answer: I feel that 3 is the answer
Explanation: Let there be 2 objects, A and B
A is at height of 5m whereas B is at height of 15m
so over here let the gravitational potential energy of A be x
and since B is 3 times higher than A B=3x
Since, earth is considered to be the point where gravitational potenial is 0
So hence forth and object 3 times up will have 3 times the gravitational potential energy of A