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: two trains of equal length , running with the speeds of 60 and 90 kmph , take 50 seconds to cross each other while they are running in the same direction . what time will they take to cross each other if they are running in opposite directions ?
Options: a ) 3.2 , b ) 2.6 , c ) 6.6 , d ) 32.2 , e ) 42.2
Example Output: c

Example Input: Problem: a train running at the speed of 120 km / hr crosses a pole in 18 seconds . what is the length of the train ?
Options: a ) 560 , b ) 570 , c ) 580 , d ) 590 , e ) 600
Example Output: e

Example Input: Problem: a man takes twice as long to row a distance against the stream as to row the same distance in favour of the stream . the ratio of the speed of the boat in still water and stream is
Options: a ) 3 : 1 , b ) 1 : 3 , c ) 2 : 4 , d ) 4 : 2 , e ) none of these
Example Output:
a