A, B, K start from the same place and travel in the same direction at speeds of 30 km/hr, 40 km/hr, 80 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?  Select:
A) 2	B) 3	C) 4	D) 5	E) 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 3 hours to travel 240 km, so C leaves 5 hours after A.   The answer is 5.
<result>D</result>
A, B, K start from the same place and travel in the same direction at speeds of 30 km/hr, 40 km/hr, 80 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?