For mice that are either homozygous dominant (pp) or heterozygous (pp), the organism's fur color is dictated by the other three genes (a/a, b/b, and c/c).
for mice that are homozygous recessive (pp), large patches of the organism's fur are white. this condition is called piebaldism.
in a cross between two mice that are heterozygous for agouti, black, color, and piebaldism, what is the probability that offspring will have solid black fur along with large patches of white fur?

The answer is 1/4 of the offspring will have solid color, 3/4 of the offspring will have black fur,  3/4 will probably have colored fur, and 1/4 of the mice offspring wil probably have pieblad, or white patches. The combined probability is  1/4 X 3/4 X 3/4 X 1/4 = 9/256.

Explanation:

Because each gene segregates independently, so you need to determime the probability of each genotype independently and then multiply the four probabilities together. The probability of offspring with solid color (aa) is 1/4; the probality of offspring  with black fur (BB or Bb) is 3/4; the probability of colored fur (Cc or cc) is 3/4, and the probability of piebald, or white patches(pp), is 1/4.   The combined probability is  1/4 X 3/4 X 3/4 X 1/4 = 9/256.