You will be given a definition of a task first, then some input of the task.
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: john traveled 80 % of the way from yellow - town to green - fields by train at an average speed of 80 miles per hour. the rest of the way john traveled by car at an average speed of v miles per hour. if the average speed for the entire trip was 70 miles per hour, what is v in miles per hour ?
Options: a. 30, b. 40, c. 50, d. 55, e. 60
Output:
e