Statistics Question

5 dogs is to be selected from a group of 12 dogs, of which 4 male and 8 female.
The expectation of selecting a male dog, E(X) = a and Var(X) = b. Independently, 4 dogs is to be selected from another group of 10 dogs of which 6 male and 4 female. The expectation of selecting a male dog, E(Y) = m and Var(Y) = n. What is the expectation and variance of the total number of male dogs in the combined selection of 9 dogs? Is it E(combined) = a + m and Var(combined) = b + n ? Please prove.