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_12 -> ~p_1. u <-> w. u <-> p_12. p_1.
~p_12 can be inferred via the modus tollens rule. u -> w can be inferred via the biconditional elimination rule. u -> p_12 can be inferred via the biconditional elimination rule. w -> u can be inferred via the biconditional elimination rule. p_12 -> u can be inferred via the biconditional elimination rule.