Product shares of a free radical reaction

You will finish a program that predicts the mix of monohalogen products from the number of hydrogen atoms at each position and the reactivity of each kind of hydrogen. The molecule is 2-methylbutane.

The idea. A product is formed in proportion to the number of hydrogen atoms at that position times the reactivity of one of them. The shares add to 100 percent.

Your tasks.

1. Complete shares(counts, reactivity) so that it returns a dictionary of percentages, one for each product.
2. Set major to the name of the main product for chlorination.
3. Set bromo_tertiary to the percentage of the tertiary product when bromine is used.