Answer:
Potential energy, P = 500 J
Step-by-step explanation:
We have,
Weight of the box, W = 50 N
Height of the stairs, h = 10 m
It is required to find the potential energy gained by the box. The potential energy is possessed by an object due to its height. The formula of potential energy is given by :

g is acceleration due to gravity

So, the potential energy of 500 J is gained by the box.