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. u_3 <-> u. s and w.
s can be inferred via the simplification rule. w can be inferred via the simplification rule. u_3 -> u can be inferred via the biconditional elimination rule. u -> u_3 can be inferred via the biconditional elimination rule. ~u_3 can be inferred via the biconditional elimination rule.