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: u <-> p_3. ~u. t <-> q_4. ~t.
~u and ~t can be inferred via the conjunction rule. ~t and ~u can be inferred via the conjunction rule. u -> p_3 can be inferred via the biconditional elimination rule. t -> q_4 can be inferred via the biconditional elimination rule. p_3 -> u can be inferred via the biconditional elimination rule. q_4 -> t can be inferred via the biconditional elimination rule. ~p_3 can be inferred via the biconditional elimination rule. ~q_4 can be inferred via the biconditional elimination rule.