Consider the following premises. forall x: U(x) or ~S(x). forall x: S(x). Can we infer forall x: U(x) from them? If possible, name the inference rules being used at each step.
 From forall x: U(x) or ~S(x) we can infer forall x: S(x) -> U(x) via universal rewriting. Finally, from forall x: S(x) -> U(x), forall x: S(x) we can infer forall x: U(x) via universal modus ponens. Therefore, the answer is yes.