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: two trains each 180 m in length are running on the same parallel lines in opposite directions with the speed of each 80 kmph. in what time will they cross each other completely ?
Options: a. 7.8 sec, b. 8.1 sec, c. 8.3 sec, d. 8.2 sec, e. 8.4 sec
b