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 180 m and 160 m long run at the speed of 60 km / hr and 40 km / hr respectively in opposite directions on parallel tracks . the time which they take to cross each other is ? 
Options: a ) 10.7 , b ) 10.9 , c ) 10.24 , d ) 12.24 , e ) 18.8
Example Output: d

Example Input: Problem: a horse chases a pony 8 hours after the pony runs . horse takes 12 hours to reach the pony . if the average speed of the horse is 320 kmph , what s the average speed of the pony ? 
Options: a ) 182 kmph , b ) 192 kmph , c ) 193 kmph , d ) 196 kmph , e ) 190 kmph
Example Output: b

Example Input: Problem: a pump can fill a tank with a water in 2 hours . because of a leak , it took 2 and 4 / 5 hours to fill the tank . the leak can drain all the water of the full tank in how many hours ? 
Options: a ) 4 , b ) 5 , c ) 6 , d ) 7 , e ) 8
Example Output:
d