What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? Name the inference rule being used: w_2 -> u. ~u. p_13 <-> q_13. w_2 or q_13.
~w_2 can be inferred via the modus tollens rule. p_13 -> q_13 can be inferred via the biconditional elimination rule. q_13 -> p_13 can be inferred via the biconditional elimination rule.