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_1 -> p_4. ~u. p_4 <-> w. u or ~w.
~w can be inferred via the disjunctive syllogism rule. w -> u can be inferred via the rewriting rule. p_4 -> w can be inferred via the biconditional elimination rule. w -> p_4 can be inferred via the biconditional elimination rule.