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 can do a piece of work in 4 hours ; b and c together can do it in 3 hours , which a and c together can do it in 2 hours . how long will b alone take to do it ?
Options: a ) 15 hours , b ) 14 hours , c ) 12 hours , d ) 74 hours , e ) 79 hours

Ex Output:
c

Ex Input:
Problem: a train of length 250 m runs at a speed of 70 km / hr . what will be the time taken to cross any stationary object standing at the railway station ?
Options: a ) 20 sec , b ) 17.23 sec , c ) 12.86 sec , d ) 9.5 sec , e ) 8.5 sec

Ex Output:
c

Ex Input:
Problem: if the population of a certain country increases at the rate of two person every 60 seconds , by how many persons does the population increase in 100 minutes ?
Options: a ) 120 , b ) 150 , c ) 240 , d ) 220 , e ) 200

Ex Output:
e