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: 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

[EX Q]: Problem: in what time will a train 50 m long cross an electric pole, it its speed be 360 km / hr ?
Options: a. 0.25, b. 0.5, c. 1.5, d. 2.5, e. 3.5
[EX A]: b

[EX Q]: Problem: two cubes have their volumes are in the ratio 1: 27. find the ratio of their surface area ?
Options: ['a. 1: 2', 'b. 2: 3', 'c. 1: 9', 'd. 2: 7', 'e. 3: 11']
[EX A]:
c