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 300 m long train crosses a platform in 45 sec while it crosses a signal pole in 18 sec . what is the length of the platform ? 
Options: a ) 287 , b ) 350 , c ) 828 , d ) 450 , e ) 122
Example Output: d

Example Input: Problem: a hall 36 m long and 15 m broad is to be paved with stones , each measuring 8 dm by 5 dm . the number of stones required is : 
Options: a ) 180 , b ) 1800 , c ) 18 , d ) 18000 , e ) 1350
Example Output: e

Example Input: Problem: in what time will a train 400 meters long cross an electric pole , if its speed is 144 km / hr 
Options: a ) 5 seconds , b ) 4.5 seconds , c ) 10 seconds , d ) 2.5 seconds , e ) none of these
Example Output:
c