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: the sum of 4 consecutive even numbers is 140 . what would be the smallest number ? 
Options: a ) 32 , b ) 88 , c ) 70 , d ) 123 , e ) 12
Example Output: a

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: an electric pump can fill a tank in 10 hours . because of a leak in the tank , it took 20 hours to fill the tank . if the tank is full , how much time will the leak take to empty it ? 
Options: a ) 10 hours , b ) 12 hours , c ) 20 hours , d ) 5 hours , e ) 15 hours
Example Output:
c