Consider the following premises. forall x: ~U_3(x). forall x: W(x) <-> S(x). forall x: W(x) or U(x). forall x: S(x) <-> U_3(x). Can we infer exists x: ~U(x) from them?
 From forall x: S(x) <-> U_3(x), forall x: ~U_3(x) we can infer forall x: ~S(x). From forall x: W(x) <-> S(x), forall x: ~S(x) we can infer forall x: ~W(x). Finally, from forall x: W(x) or U(x), forall x: ~W(x) we can infer forall x: U(x), which contradicts exists x: ~U(x). Therefore, the answer is no.