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: a starts a business with $ 3500. after 5 months, b joins with a as his partner. after a year, the profit is divided in the ratio 2: 3. b ' s contribution in the capital is
Options: a. 7000, b. 9000, c. 8000, d. 9900, e. 7900
A:
b