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'.

Ex Input:
Problem: a train passes a station platform in 31 sec and a man standing on the platform in 20 sec . if the speed of the train is 54 km / hr . what is the length of the platform ?
Options: a ) 228 , b ) 240 , c ) 165 , d ) 166 , e ) 1811

Ex Output:
c

Ex Input:
Problem: how many seconds will a train 110 meters long take to cross a bridge 150 meters long if the speed of the train is 36 kmph ?
Options: a ) 28 sec , b ) 23 sec , c ) 24 sec , d ) 25 sec , e ) 26 sec

Ex Output:
e

Ex Input:
Problem: if the population of a certain country increases at the rate of one person every 15 seconds , by how many persons does the population increase in 25 minutes ?
Options: a ) 80 , b ) 100 , c ) 150 , d ) 240 , e ) 300

Ex Output:
b