Consider the following premises. W(b) <-> u. u or ~W(b). forall y: ~W(y). Can we infer ~u from them? If possible, name the inference rules being used at each step.
 From forall y: ~W(y) we can infer ~W(b) via universal instantiation. From u or ~W(b) we can infer W(b) -> u via rewriting. From W(b) <-> u we can infer u -> W(b) via biconditional elimination. From W(b) -> u, u -> W(b) we can infer W(b) <-> u via biconditional introduction. Finally, from W(b) <-> u, ~W(b) we can infer ~u via biconditional elimination. Therefore, the answer is yes.