for #1 it is bb for brown since it is recessive and Bb for black since it is dominant. For #2, 3,4,and 5: when you do the Punnett square thing, it will be : Bb, Bb, bb, and bb. bb is for the light colored mice/rats and Bb for the dark mice. #6 is Bb, #7 none of the genotypes were purebred, #8 if both parents were brown then they would only have brown offspring, #9 both of the offspring are heterozygous black, #10 both of the offspring are homozygous brown