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: a certain sum is invested at simple interest at 18 % p. a. for two years instead of investing at 12 % p. a. for the same time period. therefore the interest received is more by rs. 300. find the sum ?
Options: a. 7000, b. 2500, c. 2778, d. 2800, e. 2791
[A]: b


[Q]: Problem: the h. c. f. of two numbers is 30 and the other two factors of their l. c. m. are 15 and 12. the larger of the two numbers is
Options: a. 476, b. 399, c. 450, d. 322, e. none
[A]: c


[Q]: Problem: a shipment of 230 smartphones contains 84 that are defective. if a customer buys two smartphones at random from the shipment, what is the approximate probability that both phones are defective ?
Options: a. 1 / 250, b. 1 / 84, c. 1 / 11, d. 9 / 68, e. 1 / 3
[A]:
d