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

[EX Q]: Problem: a person ' s present age is two - fifth of the age of his mother. after 8 years, he will be one - half of the age of his mother. how old is the mother at present
Options: a. 38, b. 40, c. 42, d. 44, e. 45
[EX A]: b

[EX Q]: Problem: the mean daily profit made by a shopkeeper in a month of 30 days was rs. 350. if the mean profit for the first fifteen days was rs. 255, then the mean profit for the last 15 days would be
Options: a. rs. 200, b. rs. 445, c. rs. 275, d. rs. 425, e. none of these
[EX A]:
b