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 20 kmph and downstream at 60 kmph , and then find the speed of the man in still water ?
Options: a ) 32 kmph , b ) 34 kmph , c ) 30 kmph , d ) 45 kmph , e ) 40 kmph
Example Output: e

Example Input: Problem: a train 280 m long , running with a speed of 72 km / hr will pass a tree in
Options: a ) 14 sec , b ) 15 sec , c ) 16 sec , d ) 20 sec , e ) none
Example Output: a

Example Input: Problem: in one hour , a boat goes 13 km along the stream and 5 km against the stream . the speed of the boat in still water ( in km / hr ) is :
Options: a ) 2 , b ) 4 , c ) 9 , d ) 12 , e ) 15
Example Output:
c