Consider the following premises. exists z: W(z) or S_2(z). forall z: S_2(z) <-> U_3(z). forall z: W(z) -> U_3(z). Can we infer exists z: W(z) or S_2(z) from them? If possible, name the inference rules being used at each step.
That is one of the premises. Therefore, the answer is yes.