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 cistern is normally filled in 10 hrs , but takes 2 hrs longer to fill because of a leak on its bottom , if cistern is full , how much time citern would empty ? 
Options: a ) 10 hours , b ) 20 hours , c ) 60 hours , d ) 40 hours , e ) 50 hours
Example Output: c

Example Input: Problem: a cyclist bikes x distance at 8 miles per hour and returns over the same path at 10 miles per hour . what is the cyclist ' s average rate for the round trip in miles per hour ? 
Options: a ) 8.1 , b ) 8.9 , c ) 8.6 , d ) 8.3 , e ) 9.0
Example Output: b

Example Input: Problem: x can finish a work in 20 days . y can finish the same work in 16 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 ) 3 , c ) 9 , d ) 5 , e ) 8
Example Output:
d