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: when positive integer n is divided by 7, the remainder is 1. when n is divided by 11, the remainder is 5. what is the smallest positive integer k such that k + n is a multiple of 77 ?
Options: a. 2, b. 4, c. 6, d. 8, e. 10

A: c
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Q: Problem: a student travels from his house to school at 10 km / hr and reaches school 2 hours late. the next day he travels 18 km / hr and reaches school 1 hour early. what is the distance between his house and the school ?
Options: a. 65.0, b. 67.5, c. 70.0, d. 72.5, e. 75.0

A: b
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Q: Problem: 5 20 380 144020 ?
Options: a. 20741616380, b. 20841616380, c. 21741616380, d. 22741616380, e. 20791616380

A:
a
****