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_3 -> u_1. ~u_1. s <-> p_4. ~s.
~u_3 can be inferred via the modus tollens rule. ~u_1 and ~s can be inferred via the conjunction rule. ~s and ~u_1 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.