Determine the genotypes of rooster and three hens | Homework Help

Two genes combine to generate the phenotype of the comb of a rooster. The 4 possible phenotypes are walnut, rose, pea and single. Rose has an absolute requirement for the presence of the dominant allele R and pea has an absolute requirement for the presence of the dominant allele P. Some of the chickens below may carry the corresponding recessive alleles r and p in the heterozygous or homozygous from (the somatic cells of chickens are diploid). A walnut comb rooster is mated to three hens. Hen A is a walnut comb and has offspring in the ratio of 3 walnut to 1 rose. Hen B is a pea comb and has offspring in the ratio 3 walnut, 3 pea, 1 rose and 1 single comb. Hen C is a walnut comb and has only walnut comb offspring. What are the genotypes of the rooster and the 3 hens? The answers are Rooster = RrPp ; Hen A = RRPp; Hen B = rrPp; Hen C = RRPP. I just can’t see how these answers came about. Any help will be truly appreciated.