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: what is the value of ( 2 ) ^ - 3 ?
Options: a. 1 / 6, b. 1 / 5, c. 1 / 8, d. 1 / 9, e. 1 / 7
[EX A]: c

[EX Q]: Problem: lloyd normally works 7.5 hours per day and earns $ 3.50 per hour. for each hour he works in excess of 7.5 hours on a given day, he is paid 1.5 times his regular rate. if lloyd works 10.5 hours on a given day, how much does he earn for that day ?
Options: a. $ 33.75, b. $ 42.00, c. $ 51.75, d. $ 54.00, e. $ 70.00
[EX A]: b

[EX 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. 840. find the sum ?
Options: a. 7000, b. 2787, c. 2799, d. 2699, e. 2790
[EX A]:
a