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: how much more would rs. 10000 fetch, after two years, if it is put at 20 % p. a. compound interest payable half yearly than if is put at 20 % p. a. compound interest payable yearly ?
Options: a. 241, b. 725, c. 992, d. 837, e. 923
[EX A]: a

[EX Q]: Problem: bottle r contains 350 capsules and costs $ 6.25. bottle t contains 130 capsules and costs $ 2.99. what is the difference between the cost per capsule for bottle r and the cost per capsule for bottle t ?
Options: a. $ 0.25, b. $ 0.12, c. $ 0.0052, d. $ 0.003, e. $ 0.002
[EX A]: c

[EX Q]: Problem: what is the units digit of ( 147 ^ 17 ) ^ 47 ?
Options: a. 1, b. 3, c. 5, d. 7, e. 9
[EX A]:
b