A poll was taken of 100 students at a commuter campus to find out how they got to campus. The results are below.

43 said they drove alone.
34 rode in a carpool.
28 rode public transportation.
4 used both carpools and public transportation.
7 used both a carpool and sometimes their own cars.
6 used buses as well as their own cars.
2 used all three methods.

How many are using all three?
_____ students

"2 used all three methods."