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 upstream at 15 kmph and downstream at 25 kmph , and then find the speed of the man in still water ? 
Options: a ) 27 , b ) 29 , c ) 30 , d ) 20 , e ) 24
Example Output: d

Example Input: Problem: a train 605 m long is running with a speed of 60 km / hr . in what time will it pass a man who is running at 6 km / hr in the direction opposite to that in which the train is going ? 
Options: a ) 81 , b ) 16 , c ) 33 , d ) 54 , e ) 12
Example Output: c

Example Input: Problem: a boatman can row 96 km downstream in 8 hr . if the speed of the current is 4 km / hr , then find in what time will be able to cover 8 km upstream ? 
Options: a ) 6 hr , b ) 2 hr , c ) 4 hr , d ) 1 hr , e ) none of these
Example Output:
b