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: there are 17 stations between hyderabad and bangalore . how many second class tickets have to be printed , so that a passenger can travel from any station to any other station ? 
Options: a ) 156 , b ) 167 , c ) 157 , d ) 342 , e ) 380

Ex Output:
d


Ex Input:
Problem: a and b complete a work in 4 days . a alone can do it in 6 days . if both together can do the work in how many days ? 
Options: a ) 3.75 days , b ) 3.7 days , c ) 3.6 days , d ) 2.4 days , e ) 5.75 days

Ex Output:
d


Ex Input:
Problem: a person can swim in still water at 20 km / h . if the speed of water 12 km / h , how many hours will the man take to swim back against the current for 40 km ? 
Options: a ) 3 , b ) 4 , c ) 5 , d ) 6 , e ) 7

Ex Output:

c