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 tank can be filled by two pipes a and b in 60 minutes and 40 minutes respectively . how many minutes will it take to fill the tank from empty state if b is used for the first half time and then a and b fill it together for the other half . 
Options: a ) 15 mins , b ) 20 mins , c ) 25 mins , d ) 30 mins , e ) 35 mins

Ex Output:
d


Ex Input:
Problem: two passenger trains start at the same hour in the day from two different stations and move towards each other at the rate of 24 kmph and 21 kmph respectively . when they meet , it is found that one train has traveled 60 km more than the other one . the distance between the two stations is ? 
Options: a ) 288 , b ) 540 , c ) 877 , d ) 278 , e ) 178

Ex Output:
b


Ex Input:
Problem: a train 500 meters long completely crosses a 300 meters long bridge in 45 seconds . what is the speed of the train is ? 
Options: a ) 32 , b ) 28 , c ) 49 , d ) 64 , e ) 21

Ex Output:

d