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: five bells commence tolling together and toll at intervals of 2 , 4 , 6 , 8 10 seconds respectively . in 20 minutes , how many times do they toll together ? 
Options: a ) 11 , b ) 10 , c ) 15 , d ) 16 , e ) 17

Ex Output:
a


Ex Input:
Problem: calculate the speed of a boat in still water ( in km / hr ) if in one hour , the boat goes 10 km / hr downstream and 4 km / hr upstream . 
Options: a ) 7 kmph , b ) 8 kmph , c ) 9 kmph , d ) 7 kmph , e ) 6 kmph

Ex Output:
a


Ex Input:
Problem: three pipes , a , b , & c are attached to a tank . a & b can fill it in 20 & 30 minutes respectively while c can empty it in 20 minutes . if a , b & c are kept open successively for 1 minute each , how soon will the tank be filled ? 
Options: a ) 2 hours , b ) 4 hours , c ) 1 hour 30 min , d ) 5 hours , e ) 6 hours

Ex Output:

c