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.

[Q]: Problem: if n is a positive integer and n ^ 2 is divisible by 36, then the largest positive integer that must divide n is
Options: a. 6, b. 12, c. 24, d. 36, e. 48
[A]: a


[Q]: Problem: 1391 x 1391 = ?
Options: a. a. 1951609, b. b. 1951601, c. c. 1951602, d. d. 1951603, e. e. 1934881
[A]: e


[Q]: Problem: seed mixture x is 40 percent ryegrass and 60 percent bluegrass by weight; seed mixture y is 25 percent ryegrass and 75 percent fescue. if a mixture of x and y contains 40 percent ryegrass, what percent of the weight of this mixture is x ?
Options: a. 100 %, b. 33.33 %, c. 40 %, d. 50 %, e. 66.66 %
[A]:
a