What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? u_1 <-> u. w_4 <-> u_1. ~r. r <-> w_4.
u_1 -> u. w_4 -> u_1. r -> w_4. u -> u_1. u_1 -> w_4. w_4 -> r. ~w_4.