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_8: Q(x_8) -> P_8(x_8). forall x_8: Q(x_8) -> P_8(x_8). ~P_8(i_2). forall x_8: P_8(x_8) -> Q(x_8).
forall x_8: Q(x_8) <-> P_8(x_8) can be inferred via the universal biconditional introduction rule. forall x_8: Q(x_8) <-> P_8(x_8) can be inferred via the universal biconditional introduction rule. forall x_8: P_8(x_8) <-> Q(x_8) can be inferred via the universal biconditional introduction rule. forall x_8: P_8(x_8) <-> Q(x_8) can be inferred via the universal biconditional introduction rule.