Answer:
392 kJ
Step-by-step explanation:
Given that,
The total mass of the cabin and the passengers = 800 kg
The vertical distance between B and C is 50 m.
We need to find the increase of gravitational potential energy of the cabin and passengers when they move from B to C. It can be given by the relation as follows :

So, the increase in gravitational potential energy is 392 kJ.