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_12: P_4(x_12) -> S_12(x_12). S_12(a_12) <-> P_4(a_12).
S_12(a_12) -> P_4(a_12) can be inferred via the biconditional elimination rule. P_4(a_12) -> S_12(a_12) can be inferred via the biconditional elimination rule.