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: find the smallest number that should be multiplied with 54000 to make it a perfect cube.
Options: ['a. 4', 'b. 5', 'c. 6', 'd. 3', 'e. 7']
[EX A]: a

[EX Q]: Problem: 30 pens and 75 pencils were purchased for 750. if the average price of a pencil was 2.00, find the average price of a pen.
Options: a. 20, b. 11, c. 12, d. 13, e. 14
[EX A]: a

[EX Q]: Problem: 3 ltr of water is added with 9 ltr of a solution containing 57 % of alcohol in the water. the % of alcohol in the new mixture is ?
Options: a. 41.5 %, b. 42.75 %, c. 43 %, d. 45 %, e. 45.75 %
[EX A]:
b