What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? r -> w_3. r or w_1. w_4 -> ~w_3. w_1 <-> w_3. u <-> w_4.
w_1 -> w_3. u -> w_4. w_3 -> w_1. w_4 -> u.