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: p_11 -> u. W(f) <-> u. forall z: ~W(z). u -> p_11.
p_11 <-> u can be inferred via the biconditional introduction rule. u <-> p_11 can be inferred via the biconditional introduction rule. W(f) -> u can be inferred via the biconditional elimination rule. u -> W(f) can be inferred via the biconditional elimination rule.