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: if 8 people take an hour to complete a piece of work , then how long should 16 people will take to complete the same piece of work ? 
Options: a ) 15 min , b ) 30 min , c ) 26 min , d ) 28 min , e ) 18 min

Ex Output:
b


Ex Input:
Problem: mary can do a piece of work in 28 days . rosy is 40 % more efficient than mary . the number of days taken by rosy to do the same piece of work is ? 
Options: a ) 22 , b ) 24 , c ) 20 , d ) 25 , e ) 27

Ex Output:
c


Ex Input:
Problem: a man can do a piece of work in 5 days , but with the help of his son , he can do it in 4 days . in what time can the son do it alone ? 
Options: a ) 15 , b ) 17 , c ) 20 , d ) 8 , e ) 9

Ex Output:

c