Consider the following premises. ~p_13. q <-> p. ~q. p_13 or u. Can we infer p from them? If possible, name the inference rules being used at each step.
 From p_13 or u, ~p_13 we can infer u via disjunctive syllogism. Finally, from q <-> p, ~q we can infer ~p via biconditional elimination, which contradicts p. Therefore, the answer is no.