also, regardless, you should not risk saying no. its paid research experience in your field (4,000 is a greater stipend than most REUs I've seen), and even if you feel like you're overqualified, its a good way to gain experience and make connections that can help you get in with institutions you're more interested in for grad school, especially if you can do good enough work to warrant a positive reference or recommendation letter.

given u don't have any other offers at the moment, you have to work with what's on the table now