What is the gravitational potential energy of the 6 kg cart as it sits the top of the incline?

There are some missing details in the question. Found them on internet:
- the mass of the cart is m=40 kg
- The height of the incline is h=300 m (see attached figure)

Solution: 
the gravitational potential energy of an object is given by

where 
m is the mass of the object
g is the gravitational acceleration
h is the height of the object above the reference point (usually taken as the ground)

By applying this formula, we find the potential energy of the cart at the top of the incline:

Ithink your answer is d