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 running at the speed of 54 km / hr crosses a pole in 7 seconds . find the length of the train . 
Options: a ) 150 meter , b ) 105 meter , c ) 140 meter , d ) 135 meter , e ) none of these

Ex Output:
b


Ex Input:
Problem: a man can do a piece of work in 4 days , but with the help of his son he can do it in 3 days . in what time can the son do it alone ? 
Options: a ) 12 days , b ) 6 days , c ) 5 days , d ) 4 days , e ) none of these

Ex Output:
a


Ex Input:
Problem: a train 150 m long can cross an electric pole in 3 sec and then find the speed of the train ? 
Options: a ) 180 , b ) 120 , c ) 72 , d ) 27 , e ) 28

Ex Output:

a