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: if teena is driving at 55 miles per hour and is currently 7.5 miles behind joe , who is driving at 40 miles per hour in the same direction then in how many minutes will teena be 45 miles ahead of joe ? 
Options: a ) 15 , b ) 60 , c ) 75 , d ) 90 , e ) 210

Ex Output:
e


Ex Input:
Problem: the time taken by a man to row his boat upstream is twice the time taken by him to row the same distance downstream . if the speed of the boat in still water is 24 kmph , find the speed of the stream ? 
Options: a ) 18 kmph , b ) 6 kmph , c ) 8 kmph , d ) 10 kmph , e ) 12 kmph

Ex Output:

c