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 x: S_3(x) -> U(x). exists x: U(x) -> S_3(x). forall x: S_3(x).
forall x: U(x) can be inferred via the universal modus ponens rule. exists x: U(x) <-> S_3(x) can be inferred via the existential biconditional introduction rule. exists x: S_3(x) <-> U(x) can be inferred via the existential biconditional introduction rule.