Consider the following premises. p <-> w. forall z: S(z). p -> ~S(f). Can we infer ~w from them? If possible, name the inference rules being used at each step.
 From forall z: S(z) we can infer S(f) via universal instantiation. From p -> ~S(f), S(f) we can infer ~p via modus tollens. Finally, from p <-> w, ~p we can infer ~w via biconditional elimination. Therefore, the answer is yes.