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: fred and sam are standing 55 miles apart and they start walking in a straight line toward each other at the same time. if fred walks at a constant speed of 6 miles per hour and sam walks at a constant speed of 5 miles per hour, how many miles has sam walked when they meet ?
Options: a. 5, b. 9, c. 25, d. 30, e. 45
A:
c