T ㅏ (A → B) ∨ (B → A). Give a formal proof of the following theorem.

Question

-((A → B) ∨ (B → A)) :AS A-> B :AS (A → B) ∨ (B → A) :/I2 | :-E1,3 -(A->B) :X4 B :AS -A :AS A :AS (A → B) ∨ (B → A) :/I This is what I have so far, I don't know what to do next.