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: a boat covers a certain distance downstream in 1 hour , while it comes back in 1 ½ hours . if the speed of the stream be 3 kmph , what is the speed of the boat in still water ? 
Options: a ) 12 kmph , b ) 13 kmph , c ) 14 kmph , d ) 15 kmph , e ) none
Example Output: d

Example Input: Problem: how many seconds will a 1200 m long train take to cross a man walking with a speed of 3 km / hr in the direction of the moving train if the speed of the train is 63 km / hr ? 
Options: a ) 26 sec , b ) 65 sec , c ) 55 sec , d ) 19 sec , e ) 72 sec
Example Output: e

Example Input: Problem: a can do a piece of work in 20 days and b can do it in 30 days and c can do it 10 days . they started the work together and a leaves after 2 days and c leaves after 4 days from the beginning . how long will work lost ? 
Options: a ) 13 , b ) 16 , c ) 25 , d ) 14 , e ) 15
Example Output:
e