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: ram , who is half as efficient as krish , will take 24 days to complete a task if he worked alone . if ram and krish worked together , how long will they take to complete the task ? 
Options: a ) 16 days , b ) 12 days , c ) 8 days , d ) 6 days , e ) 18 days

Ex Output:
c


Ex Input:
Problem: noelle walks from point a to point b at an average speed of 6 kilometers per hour . at what speed , in kilometers per hour , must noelle walk from point b to point a so that her average speed for the entire trip is 7 kilometers per hour ? 
Options: a ) 6.75 , b ) 7 , c ) 7.25 , d ) 7.5 , e ) 8.4

Ex Output:
e


Ex Input:
Problem: 12 persons can complete the work in 18 days . after working for 6 days , 4 more persons added to complete the work fast . in how many more days they will complete the work ? 
Options: a ) 10 days , b ) 9 days , c ) 8 days , d ) 7 days , e ) 6 days

Ex Output:

b