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.
Problem:Problem: arnold and danny are two twin brothers that are celebrating their birthday. the product of their ages today is smaller by 15 from the product of their ages a year from today. what is their age today ?
Options: a. 2., b. 4., c. 5., d. 7., e. 9.
Solution:
d