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: edward earns $ 7.00 per hour for the first 40 hours he works per week , and twice this rate for overtime . if michael earned $ 210 last week , how many hours did he work ?
Options: a ) 43 , b ) 44 , c ) 45 , d ) 46 , e ) 47

Ex Output:
c

Ex Input:
Problem: a train running at the speed of 50 km / hr crosses a pole in 9 seconds . find the length of the train ?
Options: a ) 125 , b ) 272 , c ) 278 , d ) 277 , e ) 112

Ex Output:
a