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: if the population of a certain country increases at the rate of one person every 15 seconds, by how many persons does the population increase in 25 minutes ?
Options: a. 80, b. 100, c. 150, d. 240, e. 300
b

Problem: at a certain university, 65 % of the professors are women, and 70 % of the professors are tenured. if 90 % of the professors are women, tenured, or both, then what percent of the men are tenured ?
Options: a. 25, b. 37.5, c. 50, d. 62.5, e. 75
d

Problem: if the sides of a cube are in the ratio 9: 7. what is the ratio of their diagonals ?
Options: a. 4: 3, b. 16: 9, c. 9: 7, d. 3: 4, e. 3: 8
c