Task: Question Answering
Input (English): Problem: a , b , k start from the same place and travel in the same direction at speeds of 30 km / hr , 40 km / hr , 160 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 ? 
Options: a ) 5.0 , b ) 5.5 , c ) 6.0 , d ) 6.5 , e ) 7.0
Output (English): d