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 man can row downstream at 16 kmph and upstream at 10 kmph . find the speed of the man in still water and the speed of stream respectively ? 
Options: a ) 3 , b ) 5 , c ) 6 , d ) 4 , e ) 9
Example Output: a

Example Input: Problem: what is the maximum number of pieces of birthday cake of size 5 ” by 5 ” that can be cut from a cake 15 ” by 15 ” ? 
Options: a ) 5 , b ) 10 , c ) 16 , d ) 20 , e ) 9
Example Output: e

Example Input: Problem: a train 210 metres long is moving at a speed of 25 kmph . it will cross a man coming from the opposite direction at a speed of 2 km per hour in : 
Options: a ) 28 sec , b ) 32 sec , c ) 36 sec , d ) 38 sec , e ) 40 sec
Example Output:
a