In rabbits, black hair depends on a dominant allele, $B$, and brown hair on a recessive allele, $b$. Short hair is due to a dominant allele, $S,$ and long hair to a recessive allele, $s .$ If a true-breeding black short-haired male is mated with a brown long-haired female, describe their offspring. What will be the genotypes of the offspring? If two of these $\mathrm{F}_{1}$ rabbits are mated, what phenotypes would you expect among their offspring? In what proportions?