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.
--------
Question: Problem: in a group of cows and chickens, the number of legs was 12 more than twice the number of heads. the number of cows was :
Options: a. 6, b. 7, c. 10, d. 12, e. 14

Answer: a

Question: 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

Answer: c

Question: Problem: in 1982 and 1983, company b ' s operating expenses were $ 10.0 million and $ 12.0 million, respectively, and its revenues were $ 15.6 million and $ 18.8 million, respectively. what was the percent increase in company b ' s profit ( revenues minus operating expenses ) from 1982 to 1983 ?
Options: a. 3 %, b. 16 2 / 3 %, c. 25 %, d. 21 3 / 7 %, e. 60 %

Answer:
d