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: an electric pump can fill a tank in 6 hours . because of a leak in the tank , it took 12 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 ) 8 hours , d ) 5 hours , e ) 15 hours
Example Output: b

Example Input: Problem: two trains of equal length , running with the speeds of 60 and 40 kmph , take 36 seconds to cross each other while they are running in the same direction . what time will they take to cross each other if they are running in opposite directions ?
Options: a ) 10 sec , b ) 16 sec , c ) 19 sec , d ) 7.2 sec , e ) 13 sec
Example Output: d

Example Input: Problem: the length of the bridge , which a train 130 m long and traveling at 45 km / hr can cross in 30 sec is ?
Options: a ) 288 , b ) 269 , c ) 245 , d ) 888 , e ) 121
Example Output:
c