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.

Example Input: Problem: the cash realised on selling a 14 % stock is rs. 109.25, brokerage being 1 / 4 % is ?
Options: a. 366, b. 106, c. 102, d. 109, e. 122
Example Output: d

Example Input: Problem: if the ratio of two number is 6: 7 and lcm of the number is 450 then what is the number.
Options: a. 11, b. 20, c. 25, d. 30, e. 35
Example Output: a

Example Input: Problem: a man purchased earphone on friday. but he forgot how much it cost. the data he have are mean expenditure of all 7 days is 500. expenditure on mon, tue, wed, thurs, sat, sun are 450600, 400500, 550300. on friday he purchased 3 things one earphone, one pen and one notebook. pen cost 30 and notebook cost 50. then what is cost of earphone ?
Options: a. 620, b. 530, c. 450, d. 470, e. 500
Example Output:
a