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: a train 124 m long running at 68 kmph crosses a platform in 19 sec. what is the length of the platform ?
Options: a. 338, b. 234, c. 240, d. 881, e. 271
b