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 mean of 50 observations is 200. but later he found that there is decrements of 34 from each observations. what is the the updated mean is ?
Options: a. 165, b. 166, c. 190, d. 198, e. 199
[EX A]: b

[EX Q]: Problem: if n = 2 ^ 0.15 and n ^ b = 1, b must equal
Options: a. 3 / 80, b. 20 / 3, c. 4, d. 5 / 3, e. 80 / 3
[EX A]: b

[EX Q]: Problem: right now, the ratio between the ages of sandy and molly is 4: 3. after 6 years, sandy ' s age will be 38 years. what is molly ' s age right now ?
Options: a. 15, b. 18, c. 21, d. 24, e. 27
[EX A]:
d