A and B start from the same point and in the same direction at 7 a.m. to walk around a rectangular field 400 m × 300 m. A and B walk at the rate of 3 km/hr and 2.5 km/hr respectively. How many times shall they cross each other if they continue to walk till 1 and 2.30 p.m.?

1. (a)Not even once
2. (b)Once
3. (c)Twice
4. (d)Thrice