Given that the elevator can only hold 4 people and that "people" could be either men "M" or woman "W", the possible combinations are as follows
WWWW = 0 men, 4 women = (0,4)
MWWW = 1 man, 3 women = (1,3)
MMWW = 2 men, 2 women = (2,2)
MMMW = 3 men, 1 woman = (3,1)
MMMM = 4 men, 0 woman = (4,0)
