What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? Name the inference rule being used: forall y: ~U_2(y). forall y: W(y) -> U(y). forall y: U_2(y) -> W(y). exists y: U(y) -> U_2(y).
exists y: ~U(y) can be inferred via the existential modus tollens rule. forall y: U_2(y) -> U(y) can be inferred via the universal transitivity rule. exists y: U(y) -> W(y) can be inferred via the existential transitivity rule. exists y: W(y) -> U_2(y) can be inferred via the existential transitivity rule.