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: the average of first 10 natural numbers is ?
Options: a. 5.6, b. 5.5, c. 5.1, d. 5.8, e. 5.2
[A]: b


[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
[A]: b


[Q]: Problem: in a sports club with 80 members, 48 play badminton and 46 play tennis and 7 do not play either. how many members play both badminton and tennis ?
Options: ['a. 23', 'b. 21', 'c. 20', 'd. 26', 'e. 27']
[A]:
b