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 is 410 meter long is running at a speed of 45 km / hour . in what time will it pass a bridge of 140 meter length 
Options: a ) 20 seconds , b ) 44 seconds , c ) 40 seconds , d ) 50 seconds , e ) none of these
Example Output: b

Example Input: Problem: how long does a train 90 m long traveling at 60 kmph takes to cross a bridge of 170 m in length ? 
Options: a ) sec , b ) sec , c ) sec , d ) sec , e ) sec
Example Output: d

Example Input: Problem: if 4 men can paint 60 m long wall in 3 days , then 5 men can paint 50 m long wall in 
Options: a ) 3 days , b ) 2 days , c ) 5 days , d ) 6 days , e ) 1 day
Example Output:
b