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'.

Example Input: Problem: in what time will a train 100 metres long cross an electric pole , if its speed be 144 km / hr ? 
Options: a ) 2.5 sec , b ) 4.25 sec , c ) 5 sec , d ) 12.5 sec , e ) none
Example Output: a

Example Input: Problem: tom drives from town q to town b , driving at a constant speed of 60 miles per hour . from town b tom immediately continues to town c . the distance between q and b is twice the distance between b and c . if the average speed of the whole journey was 36 mph , then what is tom ' s speed driving from b to c in miles per hour ? 
Options: a ) 12 , b ) 20 , c ) 24 , d ) 30 , e ) 36
Example Output: b

Example Input: Problem: a and b can do a piece of work in 11 days . with the help of c they finish the work in 5 days . c alone can do that piece of work in ? 
Options: a ) 15.5 days , b ) 19.5 days , c ) 17.5 days , d ) 9.2 days , e ) 18.5 days
Example Output:
d