The packing calculator

You will write three small functions that turn a number of base pairs into a length, a number of turns and a number of nucleosomes.

The idea. Each base pair adds $0.34\ \text{nm}$ to the length, 10 base pairs make a turn of the helix, and a nucleosome holds 200 base pairs.

Your tasks.

1. Finish length_mm. It gives the length of the DNA in millimetres. There are $10^6$ nm in a millimetre.
2. Finish turns. It gives the number of turns of the helix.
3. Finish nucleosomes. It gives the number of nucleosomes that the DNA can fill.