The insulin assembler

Two cultures of bacteria make chain A and chain B of insulin. You will count the insulin that they give, say which chain limits it, and work out how many bases of DNA the genes need.

The idea. One A chain and one B chain make one insulin molecule. A gene needs $3$ bases for each amino acid and $3$ more for the stop codon.

Your tasks.

1. Finish insulin_made. It gives the number of molecules that can form.
2. Finish limiting. It gives "A" if the A chains are fewer, "B" if the B chains are fewer, and "equal" if the numbers are equal.
3. Finish bases_needed. It gives the bases of one gene for a chain of amino_acids amino acids, with its stop codon.