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_2 -> u. w_4 <-> p_2. ~p_12. p_12 <-> u.
w_4 -> p_2 can be inferred via the biconditional elimination rule. p_12 -> u can be inferred via the biconditional elimination rule. p_2 -> w_4 can be inferred via the biconditional elimination rule. u -> p_12 can be inferred via the biconditional elimination rule. ~u can be inferred via the biconditional elimination rule.