If grey fur is dominant to white fur in a rabbit population, how many possible phenotypes will there be in the offspring of a cross between two heterozygous parents

Allele for gray fur is A (dominant)

Allele for white fur is a (recessive)

Genotype of heterozygous is Aa (heterozygous is gray, because its allele is dominant)

If we cross two heterozygous

Parents: Aa x Aa

F1: AA Aa Aa aa

The ratio between phenotypes is 3:1 (gray:white)

AA Aa Aa are with gray fur

aa is with white fur