There is an in class prize pool with 100 students of which 7 winners will be selected you are friends with 12 students what is probability 3 of 7 winners is your friend

The total number of outcomes is C(100, 7). The number of outcomes wherein there are 3 friends and 4 non-friends is C(12, 3) times C(88, 4). So the probility of having 3 friends selected is