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 train 150 m long crosses a platform 130 m long in 20 sec ; find the speed of the train ? 
Options: a ) 50 , b ) 60 , c ) 55 , d ) 45 , e ) 53
Example Output: a

Example Input: Problem: an engine moves at the speed of 60 kmph without any coaches attached to it . speed of the train reduces at the rate that varies directly as the square root of the number of coaches attached . when 4 coaches are attached speed decreases to 48 kmph . what will be the speed of train when 36 coaches are attached . 
Options: a ) 24 , b ) 28 , c ) 20 , d ) 32 , e ) 40
Example Output: a

Example Input: Problem: bill spends two days driving from point a to point b . on the first day , he drove 2 hours longer and at an average speed 5 miles per hour faster than he drove on the second day . if during the two days he drove a total of 680 miles over the course of 18 hours , what was his average speed on the second day , in miles per hour ? 
Options: a ) 20 , b ) 25 , c ) 28 , d ) 30 , e ) 35
Example Output:
e