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 garrison of 2000 men has provisions for 54 days . at the end of 15 days , a reinforcement arrives , and it is now found that the provisions will last only for 30 days more . what is the reinforcement ? 
Options: a ) 1800 men , b ) 3900 men , c ) 600 men , d ) 3800 men , e ) 900 men

Ex Output:
c


Ex Input:
Problem: 8 persons can build a wall 140 m long in 42 days . in how many days can 30 persons complete a similar wall 100 m long ? 
Options: a ) 12 , b ) 10 , c ) 8 , d ) 6 , e ) 5

Ex Output:
c


Ex Input:
Problem: a can complete a project in 20 days and b can complete the same project in 30 days . if a and b start working on the project together and a quits 5 days before the project is completed , in how many days total will the project be completed ? 
Options: a ) 12 , b ) 15 , c ) 18 , d ) 21 , e ) 24

Ex Output:

b