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'.

Problem: a train is 400 meter long is running at a speed of 60 km / hour . in what time will it pass a signal post ? 
Options: a ) 28 seconds , b ) 30 seconds , c ) 40 seconds , d ) 24 seconds , e ) 18 seconds

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
d