Problem 3 - GMAT Combinatorics

To form a six-people case competition team, a business school professor is to choose 3 female and 3 male students from a group of male and female students. If there are 7 male students in the group and 140 different six-student teams are possible, how many female students are there in the group?

A) 4
B) 7
C) 10
D) 14
E) 20