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_4 <-> w. t or w. ~u_4. ~t or w_1.
w or w_1 can be inferred via the resolution rule. u_4 -> w can be inferred via the biconditional elimination rule. w -> u_4 can be inferred via the biconditional elimination rule. ~w can be inferred via the biconditional elimination rule.