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: the ratio of the volumes of two cubes is 1331: 2197. what is the ratio of their total surface areas ?
Options: a. 121: 169, b. 169: 122, c. 81: 124, d. 81: 126, e. 81: 129
[EX A]: a

[EX Q]: Problem: if the average ( arithmetic mean ) of a and b is 45 and the average of b and c is 80, what is the value of c − a ?
Options: a. 25, b. 60, c. 90, d. 140, e. it can not be determined from the information given.
[EX A]: b

[EX Q]: Problem: if x * y = xy – 2 ( x + y ) for all integers x and y, then 3 * ( – 3 ) =
Options: a. – 16, b. – 9, c. – 4, d. 4, e. 16
[EX A]:
b