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.

[EX Q]: Problem: the average of first five multiples of 7 is :
Options: a. 9, b. 16, c. 15, d. 8, e. 21
[EX A]: e

[EX Q]: Problem: michelle deposited a certain sum of money in a savings account on july 1 st, 2007. she earns an 14 % interest compounded semiannually. the sum of money in the account on december 31 st, 2009 is approximately what percent of the initial deposit ?
Options: a. 117 %, b. 120 %, c. 121 %, d. 138 %, e. 145 %
[EX A]: d

[EX Q]: Problem: in one day, juan sends keith 8 times as many messages as he sends laurence, and laurence sends missy 4.5 times as many messages as he receives from juan. if missy received 18 messages from laurence, how many messages does keith receive from juan ?
Options: a. 13, b. 26, c. 32, d. 48, e. 56
[EX A]:
c