Two friends A and B simultaneously start running around a circular track . They run in the same direction

Two friends A and B simultaneously start running around a circular track . They run in the same direction. A travels at 6 m/s and B runs at b m/s. If they cross each other at exactly two points on the circular track and b is a natural number less than 30, how many values can b take?

1. 3
2. 4
3. 7
4. 5