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'.

Example Input: Problem: two trains t 1 and t 2 start simultaneously from two stations x and y respectively towards each other . if they are 70 km apart both 3 and 6 hours after start , then find the distance between the two stations . 
Options: a ) 210 km , b ) 240 km , c ) 220 km , d ) 180 km , e ) 190 km
Example Output: a

Example Input: Problem: the ratio of efficiency of a is to c is 5 : 3 . the ratio of no . of days taken by b is to c is 2 : 3 . a takes 6 days less than c , when a and c completes the work individually . b and c left the work after 2 days . the no of days taken by a to finish the remaining work ? 
Options: a ) 4.5 , b ) 5 , c ) 6 , d ) 7 , e ) 8
Example Output: c

Example Input: Problem: a motor boat takes 12 hours to go downstream and it takes 24 hours to return the same distance . what is the time taken by boat in still water ? 
Options: a ) 26 h , b ) 16 h , c ) 86 h , d ) 96 h , e ) 66 h
Example Output:
b