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.

Problem: the average age of 8 men increases by 2 years when two women are included in place of two men of ages 20 and 22 years. find the average age of the women ?
Options: a. 87, b. 98, c. 30, d. 29, e. 37
d

Problem: a clock shows the time as 9 a. m. if the minute hand gains 7 minutes every hour, how many minutes will the clock gain by 6 p. m. ?
Options: a. 30 min, b. 35 min, c. 63 min, d. 50 min, e. 55 min
c

Problem: the sum of the first n positive perfect squares, where n is a positive integer, is given by the formula n ^ 3 / 3 + c * n ^ 2 + n / 6, where c is a constant. what is the sum of the first 20 positive perfect squares ?
Options: a. 1,010, b. 1,164, c. 1,240, d. 2,316, e. 2,870

e