Help pls! 1. there are 12 students in a class. Find the number of ways to select 8 students to sit in a row of 8 seats
2. There are 5 boys and 7 girls in a class. The students must be arranged to sit in a row of 12 seats. Find the number of ways to arrange the students if
(a) the boys must sit next to each other, and the girls must sit next to each other
(b) only the girls must sit next to each other