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 speed of a boat in still water is 15 km / hr and the rate of current is 3 km / hr . the distance travelled downstream in 12 minutes is 
Options: a ) 1.2 km , b ) 1.8 km , c ) 2.4 km , d ) 3.6 km , e ) 1.6 km
Example Output: d

Example Input: Problem: to fill a tank , 25 buckets of water is required . how many buckets of water will be required to fill the same tank if the capacity of the bucket is reduced to 1 / 2 of its present ? 
Options: a ) 61.5 , b ) 60.5 , c ) 63.5 , d ) 62.5 , e ) 50
Example Output: e

Example Input: Problem: a train of length l is traveling at a constant velocity and passes a pole in t seconds . if the same train travelling at the same velocity passes a platform in 6 t seconds , then what is the length of the platform ? 
Options: a ) l , b ) 3 l , c ) 5 l , d ) 7 l , e ) 9 l
Example Output:
c