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: 6 bells commence tolling together and toll at the intervals of 24 , 68 , 1012 seconds resp . in 60 minutes how many times they will toll together . 
Options: a ) 15 , b ) 16 , c ) 30 , d ) 31 , e ) none of these

Ex Output:
d


Ex Input:
Problem: one pipe can fill a tank three times as fast as another pipe . if together the two pipes can fill the tank in 35 minutes , then the slower pipe alone will be able to fill the tank in 
Options: a ) 144 mins , b ) 140 mins , c ) 136 mins , d ) 132 minw , e ) none of these

Ex Output:

b