In this task, you need to answer the given multiple-choice question on the physics. Classify your answers into 'a', 'b', 'c', 'd', and 'e'.

Example Input: Problem: a man can row upstream at 15 kmph and downstream at 25 kmph , and then find the speed of the man in still water ? 
Options: a ) 27 , b ) 29 , c ) 30 , d ) 20 , e ) 24
Example Output: d

Example Input: Problem: two trains 120 m and 160 m long run at the speed of 60 km / hr and 40 km / hr respectively in opposite directions on parallel tracks . the time which they take to cross each other is ? 
Options: a ) 10.9 , b ) 10.7 , c ) 10.3 , d ) 10.08 , e ) 10.2
Example Output: d

Example Input: Problem: a pipe takes a hours to fill the tank . but because of a leakage it took 6 times of its original time . find the time taken by the leakage to empty the tank 
Options: a ) 50 min , b ) 60 min , c ) 72 min , d ) 80 min , e ) 70 min
Example Output:
c