Teams A,B,C participated in the championship on boxing. The each boxer from team A boxed exactly with 5 boxers from B and 2 from C, each boxer from B-with 6 from A and 4 from C, and each from C - with 3 from A and m from B. What is m?
A.3
B. 4
C. 5
D. 6
E. 7