Few Questions Regarding extension. Please Help.

[RaviWood]

I’m planning on extending my parents stay for few months for the first time. They both have the same return date on their current I-94.

Do I need to pay separate fee $290 for both of them or just $290 for both?

Is the Visa extension application fee $290 is refundable if rejected?

Is there a minimum amount of funds that I need in my bank account for purposes of extending their visa (proof of fund)?

[immihelp]

1. One time $290.
2. No. That is the processing fee.
3. There is no specific amount, but something like $5,000/person is good.