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: P_3(x) <-> S_2(x). P_3(f) <-> S_2(f).
P_3(f) -> S_2(f) can be inferred via the biconditional elimination rule. S_2(f) -> P_3(f) can be inferred via the biconditional elimination rule. forall x: P_3(x) -> S_2(x) can be inferred via the universal biconditional elimination rule. forall x: S_2(x) -> P_3(x) can be inferred via the universal biconditional elimination rule.