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: p_3 <-> r. p_3 -> r. ~r.
~p_3 can be inferred via the modus tollens rule. p_3 -> r can be inferred via the biconditional elimination rule. r -> p_3 can be inferred via the biconditional elimination rule. ~p_3 can be inferred via the biconditional elimination rule.