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: mariah has decided to hire three workers . to determine whom she will hire , she has selected a group of 12 candidates . she plans to have one working interview with 3 of the 12 candidates every day to see how well they work together . how many days will it take her to have working interviews with all the different combinations of job candidates ? 
Options: a ) 720 , b ) 120 , c ) 300 , d ) 30 , e ) 333

Ex Output:
c


Ex Input:
Problem: a boat running downstream covers a distance of 12 km in 2 hours while for covering the same distance upstream , it takes 3 hours . what is the speed of the boat in still water ? 
Options: a ) 8 kmph , b ) 5 kmph , c ) 4 kmph , d ) 6 kmph , e ) 7 kmph

Ex Output:
b


Ex Input:
Problem: if the population of a certain country increases at the rate of one person every 15 seconds , by how many persons does the population increase in 60 minutes ? 
Options: a ) 80 , b ) 100 , c ) 150 , d ) 240 , e ) 300

Ex Output:

d