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: ~p_2 or s. forall x_13: P_13(x_13) -> Q_13(x_13). forall x_13: ~Q_13(x_13). p_2 or P_13(a_8). forall x_13: Q_13(x_13) -> P_13(x_13).
P_13(a_8) or s can be inferred via the resolution rule. R_1(a_8) -> p_2 can be inferred via the rewriting rule. forall x_13: ~P_13(x_13) can be inferred via the universal modus tollens rule. forall x_13: P_13(x_13) <-> Q_13(x_13) can be inferred via the universal biconditional introduction rule. forall x_13: Q_13(x_13) <-> P_13(x_13) can be inferred via the universal biconditional introduction rule.