6 A group of 7 students sit in random order on a bench.
- (a) Find the number of orders in which they can sit.
(b) The 7 students include Tom and Jerry. Find the probability that Tom and Jerry sit next to each other. - The students consist of 3 girls and 4 boys. Find the probability that
(a) no two boys sit next to each other,
(b) all three girls sit next to each other.