The blood group tester

You will write a small program for the ABO blood groups and for a polygenic trait. An allele is written as "A", "B" or "i".

The idea. A and B are codominant, and both are dominant over i. A child gets one allele from each parent.

Your tasks.

1. Finish group. It gives the blood group ("A", "B", "AB" or "O") of a person from two alleles.
2. Finish child_groups. It gives the set of blood groups that the children of two parents can have. Each parent is a pair of alleles.
3. Finish polygenic_ways. It gives the number of the 64 boxes of the cross AaBbCc × AaBbCc that have exactly k capital alleles.