The generation counter

Bacteria with heavy DNA are moved to a light medium. You will write three functions that tell what the tube shows after any number of generations.

The idea. After $g$ generations a starting molecule has made $2^g$ molecules. Two of them are hybrid, and the rest are light. With zero generations all the DNA is still heavy.

Your tasks.

1. Finish molecules. It gives the number of molecules after g generations, from start heavy molecules.
2. Finish hybrid_percent. It gives the per cent of the molecules that are hybrid. For zero generations it gives 0.
3. Finish light_percent. It gives the per cent of light molecules. It is 0 for 0 and 1 generations.