Detailed Instructions: Given a math problem with context and a question and 5 answer choices, the task is to provide the correct answer choice based on the problem. You must choose one of the given answer choices by letter: a, b, c, d, or e; anything else is invalid.
Q: Problem: a train which has 390 m long, is running 45 kmph. in what time will it cross a person moving at 9 kmph in same direction ?
Options: a. 26 sec, b. 39 sec, c. 36 sec, d. 29 sec, e. 30 sec
A:

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
b