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: find the simple interest on rs. 72,000 at 16 2 / 3 % per year for 9 months.
Options: a. 7500, b. 6500, c. 9000, d. 9500, e. none of them

Answer: c

Question: Problem: the average of first five multiples of 7 is :
Options: a. 9, b. 16, c. 15, d. 8, e. 21

Answer: e

Question: Problem: how many multiples of 6 are less than 5000, and also multiples of 8 ?
Options: a. 104, b. 208, c. 625, d. 832, e. 833

Answer:
b