Answer:
A cross between a roan bull (Ww) and a white cow (ww) produces roan and white phenotypes in a 1:1 ratio.
Step-by-step explanation:
Two alleles are influencing the color of the hair of the cow-W red and w white.
These alleles show that a hybrid Ww has red hair. The genotype of the bull is Ww, WW is red and ww is white. So, mixing the red and white cows is 1:1.