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 20 typists can type 50 letters in 30 minutes , then how many letters will 40 typists working at the same rate complete in 1 hour ?
Options: a ) 400 , b ) 500 , c ) 350 , d ) 250 , e ) 200
Example Output: a

Example Input: Problem: a can do a work in 15 days and b in 20 days . if they work on it together for 5 days , then the fraction of the work that is left is :
Options: a ) 1 / 3 , b ) 7 / 12 , c ) 5 / 12 , d ) 2 / 3 , e ) 1 / 2
Example Output: c

Example Input: Problem: if 3 men or 4 women can reap a field in 10 days how long will 5 men and 6 women take to reap it ?
Options: a ) 19 / 60 , b ) 9 / 60 , c ) 2 / 3 , d ) 5 / 18 , e ) 6 / 24
Example Output:
a