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: u_1 -> P_12(a_11). forall x_12: P_12(x_12) -> Q_12(x_12). ~Q_12(a_11). forall x_12: Q_12(x_12) -> P_12(x_12).
forall x_12: P_12(x_12) <-> Q_12(x_12) can be inferred via the universal biconditional introduction rule. forall x_12: Q_12(x_12) <-> P_12(x_12) can be inferred via the universal biconditional introduction rule.