This is one of those colloquialisms that doesn't seem to translate to a complete sentence, but how would you properly punctuate and/or correct the following sentence?
I'd like you to keep working, but if you want to quit, then fine.
My interest is on the last phrase "then fine" which I've heard before but can't seem to figure out how to write it down properly. Is it "then fine" or "then, fine" or something else entirely?
What kind of grammatical function is it?