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 2 hours , while a and c together can do it in 2 hours . how long will b alone take to do it ?
Options: a ) 12 , b ) 9 , c ) 8 , d ) 6 , e ) 4

Ex Output:
e

Ex Input:
Problem: a and b can do a piece of work in 3 days , b and c in 4 days , c and a in 6 days . how long will c take to do it ?
Options: a ) 33 , b ) 77 , c ) 24 , d ) 55 , e ) 71

Ex Output:
c

Ex Input:
Problem: how many revolutions will a circular wheel make to travel a distance of 3 km , given that the radius is 2.4 m ?
Options: a ) 11085.7 , b ) 15085.7 , c ) 35085.7 , d ) 15015.7 , e ) 15083.7

Ex Output:
a