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 and b together can do a piece of work in 10 days . b alone can finish it in 20 days . in how many days can a alone finish the work ? 
Options: a ) 20 , b ) 10 , c ) 15 , d ) 5 , e ) 7

Ex Output:
a


Ex Input:
Problem: 13 buckets of water fill a tank when the capacity of each bucket is 51 litres . how many buckets will be needed to fill the same tank , if the capacity of each bucket is 17 litres ? 
Options: a ) 39 , b ) 28 , c ) 23 , d ) 12 , e ) 24

Ex Output:
a


Ex Input:
Problem: a man , a woman and a boy can together complete a piece of work in 3 days . if a man alone can do it in 6 days and a boy alone in 12 days , how long will a woman take to complete the work ? 
Options: a ) 12 days , b ) 10 days , c ) 9 days , d ) 8 days , e ) 11 days

Ex Output:

a