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: a trader sells 45 meters of cloth for rs . 4500 at the profit of rs . 14 per metre of cloth . what is the cost price of one metre of cloth ? 
Options: a ) rs . 80 , b ) rs . 86 , c ) rs . 90 , d ) rs . 95 , e ) none of these
Example Output: b

Example Input: Problem: a boat takes 38 hours for travelling downstream from point a to point b and coming back to point c midway between a and b . if the velocity of the stream is 4 kmph and the speed of the boat in still water is 14 kmph , what is the distance between a and b ? 
Options: a ) 240 km , b ) 120 km , c ) 360 km , d ) 180 km , e ) none of these
Example Output:
c