how to i get All possible Genotypes for two horses

In horses, the black (B) allele for hair color is dominant over the brown (b) allele and the trotter (T) allele for the two beat gait is dominant over the pacer (t) allele. A black, pacer horse mates with a brown, trotter horse producing a brown, pacer foal. Give the genotypes of all horses involved.

Black pacer horse (parent): Bbtt
Brown trotter horse (parent): bbTt
Brown pacer foal (offspring): bbtt

Explaination: The only way the offspring could display the Brown recessive gene is if it is homozygous for the trait meaning it recieved 1 copy of the 'b' allel from each parent. Therefore, the Black parent, who has the dominate phenotype Black, must be heterozygous for the trait. Also, the only way the offspring could display the pacer recessive gene is if it is homozygous for the trait meaning it recieved 1 copy of the 't' allel from each parent. Therefore, the Brown parent, who has the dominate phenotype Trotter, must be heterozygous for the trait.