Thank you for your replies! :)
After reading your posts, I realized that, clearly, I made two critical mistakes:
in general, if you're actually "plugging" specific numbers into a VERBAL problem ... don't. just don't do it.
1. Approaching this question in a wrong way
choice (e) is irrelevant because we're talking only about businesses whose clients are retired.
2. Not only approaching this question in a wrong way, but also approaching with a good amount of efforts that are unnecessary
--
I will keep your advice in mind! :)