Consider the following premises. exists z_1: Q_3(z_1). forall z_1: Q_3(z_1) -> T_4(z_1). forall z_1: T(z_1) <-> T_4(z_1). Can we infer exists z_1: T(z_1) from them?
 From forall z_1: T(z_1) <-> T_4(z_1) we can infer forall z_1: T_4(z_1) -> T(z_1). From forall z_1: Q_3(z_1) -> T_4(z_1), forall z_1: T_4(z_1) -> T(z_1) we can infer forall z_1: Q_3(z_1) -> T(z_1). Finally, from forall z_1: Q_3(z_1) -> T(z_1), exists z_1: Q_3(z_1) we can infer exists z_1: T(z_1). Therefore, the answer is yes.