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 man started driving at a constant speed , from the site of a blast , the moment he heard the blast . he heard a second blast after a time of 30 mins and 25 seconds . if the second blast occurred exactly 30 mins after the first , how many meters was he from the site when he heard the second blast ? ( speed of sound = 330 m / s ) 
Options: a ) 8250 , b ) 9350 , c ) 10,450 , d ) 11,550 , e ) 12,650
Example Output: a

Example Input: Problem: on a trip covering 400 km , a bicyclist travels the first 100 km at 20 km per hour and the remainder of the distance at 15 km per hour . what is the average speed , in km per hour , for the entire trip ? 
Options: a ) 15.5 , b ) 16.0 , c ) 16.5 , d ) 17.0 , e ) 17.5
Example Output: b

Example Input: Problem: in what time will a railway train 64 m long moving at the rate of 46 kmph pass a telegraph post on its way ? 
Options: a ) 3 , b ) 5 , c ) 4 , d ) 6 , e ) 7
Example Output:
b