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'.

Ex Input:
Problem: x can finish a work in 20 days . y can finish the same work in 15 days . yworked for 9 days and left the job . how many days does x alone need to finish the remaining work ? 
Options: a ) 3 , b ) 5 , c ) 6 , d ) 8 , e ) 9

Ex Output:
d


Ex Input:
Problem: two trains of length 100 meters and 200 meters are 840 meters apart . they are moving towards each other on parallel tracks , at speeds of 54 km / h and 72 km / h . after how many seconds will the trains meet ? 
Options: a ) 20 , b ) 22 , c ) 24 , d ) 26 , e ) 28

Ex Output:
c


Ex Input:
Problem: tap a runs 3 liters of water per minute into a bucket that has a total volume of 36 liters . tap b fills a third of the bucket in 20 mins . working together how long will it take both taps to fill the bucket ? 
Options: a ) 10 minutes , b ) 1.5 hours , c ) 9 hours and 12 minutes , d ) 15 hours , e ) 1 hour and 48 minutes .

Ex Output:

a