Potential energy on different worlds

A $6\ \text{kg}$ box is held $4\ \text{m}$ up on four worlds. You will make the program find its potential energy on each, pick out the world where it stores the most, and find how high the box must be on the Moon to store as much as on the Earth. Then it draws the energies as bars.

The idea. $PE = mgh$, so a world with a bigger $g$ stores more energy at the same height.

Your tasks.

1. Inside the loop, work out PE on each world, in joules.
2. Set most to the name of the world where the box stores the most energy.
3. Find h_moon, the height on the Moon that gives the same energy as $4\ \text{m}$ on the Earth, in metres.