Task: Question Answering
Input (English): Problem: two trains are moving in opposite directions at 60 km / hr and 90 km / hr . their lengths are 1.15 km and 0.6 km respectively . the time taken by the slower train to cross the faster train in seconds is ? 
Options: a ) 42 , b ) 9 , c ) 7 , d ) 67 , e ) 15
Output (English): a