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: x can finish a work in 25 days . y can finish the same work in 20 days . y worked for 12 days and left the job . how many days does x alone need to finish the remaining work ? 
Options: a ) 2 , b ) 5 , c ) 6 , d ) 7 , e ) 8
Example Output: e

Example Input: Problem: some persons can do a piece of work in 8 days . two times the number of these people will do half of that work in ? 
Options: a ) 2 , b ) 4 , c ) 5 , d ) 6 , e ) 8
Example Output: a

Example Input: Problem: if 20 typists can type 48 letters in 20 minutes , then how many letters will 30 typists working at the same rate complete in 1 hour ? 
Options: a ) 63 , b ) 72 , c ) 144 , d ) 216 , e ) 400
Example Output:
d