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_2: S(y_2) -> U(y_2). forall y_2: U(y_2) or ~S(y_2). exists y_2: U(y_2) -> S(y_2).
forall y_2: S(y_2) -> U(y_2) can be inferred via the universal rewriting rule. exists y_2: U(y_2) <-> S(y_2) can be inferred via the existential biconditional introduction rule. exists y_2: S(y_2) <-> U(y_2) can be inferred via the existential biconditional introduction rule.