The allele D in dogs is lethal when homozygous , but is dominant and gives dwarf legs in the heterozygous condition with d, an allele for normal legs. At a second locus affecting fur color, the alleles F1 and F2 show incomplete dominance - F1F1 homozygotes have white fur , F2F2 homozygotes have black fur, and F1F2 heterozygotes have grey fur . You perform a cross of the following dogs : dwarf legs , grey fur X dwarf legs , grey fur.

a. What is the genotype of the dogs involved in the cross ?