Task: Question Answering
Input (English): Problem: a train overtakes two persons who are walking in the same direction in which the train is going , at the rate of 2 kmph and 4 kmph and passes them completely in 9 and 10 seconds respectively . the length of the train is : 
Options: a ) 10 , b ) 100 , c ) 50 , d ) 200 , e ) 300
Output (English): c