Consider the following premises. forall y_1: ~W_4(y_1). forall y_1: U(y_1) <-> Q(y_1). forall y_1: Q(y_1) <-> W_4(y_1). Can we infer exists y_1: U(y_1) from them?
 From forall y_1: Q(y_1) <-> W_4(y_1), forall y_1: ~W_4(y_1) we can infer forall y_1: ~Q(y_1). Finally, from forall y_1: U(y_1) <-> Q(y_1), forall y_1: ~Q(y_1) we can infer forall y_1: ~U(y_1), which contradicts exists y_1: U(y_1). Therefore, the answer is no.