What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? p_7 <-> u_3. w_2. u_3 <-> r_1. p_7 -> ~w_2.
~p_7. p_7 -> u_3. u_3 -> r_1. u_3 -> p_7. r_1 -> u_3.