Consider the following premises. T(b) -> Q(b). forall z: Q(z) -> T(z). T(b) -> Q(b). Can we infer T(b) <-> Q(b) from them?
 From forall z: Q(z) -> T(z) we can infer Q(b) -> T(b). From Q(b) -> T(b), T(b) -> Q(b) we can infer Q(b) <-> T(b). From Q(b) <-> T(b) we can infer Q(b) -> T(b). Finally, from T(b) -> Q(b), Q(b) -> T(b) we can infer T(b) <-> Q(b). Therefore, the answer is yes.