In Horses, There Are Four Alleles at the a Locus

Essay

In horses, there are four alleles at the A locus.Arranged in dominance sequence they are:
A (wild), a^b (bay), a^c (brown), a^d (black)
If you bred several bay mares whose sires were brown to a brown stallion whose sire was black, what are the genotypes of the parents; what type of offspring would be produced; and in what proportion?