Consider the following premises. forall y: T(y) -> W(y). exists y: ~S_3(y). forall y: W(y) <-> S_3(y). Can we infer exists y: ~T(y) from them? If possible, name the inference rules being used at each step.
 From forall y: W(y) <-> S_3(y), exists y: ~S_3(y) we can infer exists y: ~W(y) via existential biconditional elimination. Finally, from forall y: T(y) -> W(y), exists y: ~W(y) we can infer exists y: ~T(y) via existential modus tollens. Therefore, the answer is yes.