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: 20 beavers , working together in a constant pace , can build a dam in 18 hours . how many hours will it take 12 beavers that work at the same pace , to build the same dam ?
Options: a ) 22 . , b ) 24 . , c ) 30 . , d ) 36 , e ) 38 .

Ex Output:
c

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: ajay can ride 50 km in 1 hour . in how many hours he can ride 500 km ?
Options: a ) 10 hrs , b ) 15 hrs , c ) 20 hrs , d ) 25 hrs , e ) 18 hrs

Ex Output:
a