Given the task definition and input, reply with output. 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.

Problem: brenda and sally run in opposite direction on a circular track, starting at diametrically opposite points. they first meet after brenda has run 50 meters. they next meet after sally has run 150 meters past their first meeting point. each girl runs at a constant speed. what is the length of the track in meters ?
Options: a. 250, b. 300, c. 350, d. 400, e. 500
a