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