Why was "так собі" not accepted for "ok?" I would think that "ok" and "so-so" are synonyms.
I am not a native English speaker, so I don't know how good feels the person who says "ok", but "добре" is definitely good answer, I would say "Fine!" is a good translation, while "Так собі" implies that something is wrong
Як твої справи - can be accepted too, but it`s marked wrong.