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: a boat can travel with a speed of 16 km / hr in still water . if the rate of stream is 5 km / hr , then find the time taken by the boat to cover distance of 84 km downstream .
Options: a ) 4 hours , b ) 5 hours , c ) 6 hours , d ) 7 hours , e ) 8 hours
Example Output: a

Example Input: Problem: if two girls starting from same point , walking in the opposite directions with 7 km / hr and 3 km / hr as average speeds respectively . then the distance between them after 12 hours is ?
Options: a ) 120 , b ) 121 , c ) 122 , d ) 123 , e ) 124
Example Output: a

Example Input: Problem: if the weight of 12 meters long rod is 14 kg . what is the weight of 6 meters long rod ?
Options: a ) 8 kg . , b ) 10.8 kg . , c ) 7 kg . , d ) 18.0 kg , e ) none
Example Output:
c