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: r -> q_2. p_4 or q_13. s <-> p_4. ~s. ~q_2.
~r can be inferred via the modus tollens rule. ~s and ~q_2 can be inferred via the conjunction rule. ~q_2 and ~s can be inferred via the conjunction rule. s -> p_4 can be inferred via the biconditional elimination rule. p_4 -> s can be inferred via the biconditional elimination rule. ~p_4 can be inferred via the biconditional elimination rule.