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: if 36 men can do a piece of work in 5 hours , in how many hours will 15 men do it ? 
Options: a ) 12 , b ) 38 , c ) 60 , d ) 88 , e ) 72
Example Output: a

Example Input: Problem: a and b together can do a work in 4 days . if a alone can do it in 20 days . in how many days can b alone do it ? 
Options: a ) 11 , b ) 5 , c ) 6 , d ) 8 , e ) 25
Example Output: b

Example Input: Problem: a river 3 m deep and 36 m wide is flowing at the rate of 2 kmph the amount of water that runs into the sea per minute is ? 
Options: a ) 4500 , b ) 2678 , c ) 3600 , d ) 3400 , e ) 2500
Example Output:
c