How many permutations of simple events

[waealu]

Homework Statement

I am stuck on this problem relating to permutations:

The first part asks how many ways can 6 people be lined up. This answer, I believe is 6! = 720 ways.

The second part: If 3 specific persons, among 6, insist on following each other, how many ways are possible?

The third part: If 2 specific persons, among 6, refuse to follow each other, how many ways are possible?

The first part is easy, but I don't know how to do the second and third parts. What is the concept involved in solving the second and third parts?

Thanks for the help!

 

[vela]

For the second part, just think of the three-people clump as one person, so you have four people that you need to order.