When a female golden Labrador Retriever is mated with a black male (#1), and then with a brown male (#2), what is the proportion of the resulting puppies' coat colors in the second litter?
a) 1/4 black, 1/4 brown, 1/2 golden
b) 1/4 black, 1/2 brown, 1/4 golden
c) 1/2 black, 1/4 brown, 1/4 golden
d) 1/2 black, 1/2 brown, 0 golden