In Mice, Black Coat Color Is Dominant to White Coat

Multiple Choice

In mice, black coat color is dominant to white coat color. In the pedigree below, mice with a black coat are represented by darkened symbols, and those with white coats are shown as open symbols. What is the probability that I- 1, I- 2, II- 2, AND III- 1 are all heterozygous?

A) 2/3
B) 1/2
C) 0
D) 1
E) 1/4