Detailed Instructions: 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: exactly 3 / 7 of the people in the room are under the age of 21, and exactly 5 / 10 of the people in the room are over the age of 65. if the total number of the people in the room is greater than 50 and less than 100, how many people in the room are under the age of 21 ?
Options: a. 21, b. 35, c. 39, d. 30, e. 65
A:
d