Consider the following premises. forall z_4: T(z_4) <-> R(z_4). forall z_4: U_1(z_4) <-> T(z_4). forall z_4: R(z_4) <-> U(z_4). forall z_4: ~U(z_4). Can we infer exists z_4: U_1(z_4) from them?
 From forall z_4: R(z_4) <-> U(z_4), forall z_4: ~U(z_4) we can infer forall z_4: ~R(z_4). From forall z_4: T(z_4) <-> R(z_4), forall z_4: ~R(z_4) we can infer forall z_4: ~T(z_4). Finally, from forall z_4: U_1(z_4) <-> T(z_4), forall z_4: ~T(z_4) we can infer forall z_4: ~U_1(z_4), which contradicts exists z_4: U_1(z_4). Therefore, the answer is no.