A, B, K start from the same place and travel in the same direction at speeds of 30 km/hr, 40 km/hr, 50 km/hr respectively. B starts two hours after A. If B and K overtake A at the same instant, how many hours after A did K start?  Pick:
A) 2.4
B) 3.2
C) 4.0
D) 4.8
E) 5.6
In 2 hours, A travels 60 km.   B can catch A at a rate of 10 km/hr, so B catches A 6 hours after B starts.   So A and B both travel a distance of 240 km.   C needs 4.8 hours to travel 240 km, so C leaves 3.2 hours after A.   The answer is 3.2.
<result>B</result>
A, B, K start from the same place and travel in the same direction at speeds of 30 km/hr, 40 km/hr, 50 km/hr respectively. B starts two hours after A. If B and K overtake A at the same instant, how many hours after A did K start?