-- A: Were you at the party yesterday evening?
-- B: Yes, I was there!
What should be the translation of "I was there"?
-- A: Est-ce que tu as été à la fête hier soir?
-- B: Oui, j'y ai été!
or
-- B: Oui, j'ai été là-bas!
or
-- B: Oui, j'y ai assisté!
Also, is it correct to use the passé composé here? It's a single event so I think it's the right choice, but please let me know if it should be the imparfait instead.