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: if 8 people take an hour to complete a piece of work , then how long should 16 people will take to complete the same piece of work ?
Options: a ) 15 min , b ) 30 min , c ) 26 min , d ) 28 min , e ) 18 min
Example Output: b

Example Input: Problem: a and b can do a piece of work in 2 days , b and c in 3 days , c and a in 4 days . how long will c take to do it ?
Options: a ) 14 days , b ) 20 days , c ) 22 days , d ) 24 days , e ) 26 days
Example Output:
d