Suppose that the U.S. Senate consisted of 60 Republican and 40 Democratic senators. How many different 10-person committees could be formed with 6 Republican senators and 4 Democratic senators?.

choose 6 R from the 60 R, then choose 4 D from the 40 D

= C(60,6) x C(40,4)
= huge .... ( 4.57 x 10^12)