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_2(x) -> R_1(x). forall x: R_1(x) -> S_2(x). forall x: S_2(x) -> R_1(x).
forall x: S_2(x) <-> R_1(x) can be inferred via the universal biconditional introduction rule. forall x: R_1(x) <-> S_2(x) can be inferred via the universal biconditional introduction rule. forall x: R_1(x) <-> S_2(x) can be inferred via the universal biconditional introduction rule. forall x: S_2(x) <-> R_1(x) can be inferred via the universal biconditional introduction rule.