Sets problem 13

In sport training class, 4 students are swimming, 6 playing football, and 4 playing volleyball. 3 student are swimming and playing volleyball and 2 are swimming and playing football. One of the students participates in all 3 sports. 13 students do not practice any of the listed sports. How many students are involved in at least one sport? How many students train exactly for two sports? How many students are in the class? Solve the problem with sets.