Two runners start 30 kilometers apart and run toward each other. They meet after 3 hours. One runner runs 2 kilometers per hour faster than the other runner. What rate do they run?
A. 2 km/hr and 4 km/hr
B. 3 km/hr and 5 km/hr
C. 5 km/hr and 7 km/hr
D. 4 km/hr and 6 km/hr