coat color in rats is determined by one gene with b and b alleles. rats with bb genotype have black fur and those homozygous for the b allele have white fur; heterozygotes are brown. a second gene also influences coat color such that rats which are homozygous for the recessive allele, p, are pink regardless of the alleles they carry at the b/b locus. a dihybrid cross is made; what would the expected ratio of pink rats be?