Energy up the chain

Grass in a grassland stores $60\,000$ kJ of energy. It feeds a chain of four more levels. You will list the energy at each level with the ten per cent law. Then you will find the first level that gets less than $50$ kJ, and the share of the grass's energy that reaches the top.

The idea. Each level gets a tenth of the energy of the level below.

Your tasks.

1. Set energy to the list of energies, in kJ, at the five levels, starting with the grass.
2. Set first_low to the name of the first level that gets less than $50$ kJ.
3. Set top_percent to the energy at the top as a percentage of the grass's energy.