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: exists x_13: P(x_13) -> P_9(x_13). forall x_13: ~Q_9(x_13). forall x_13: T_1(x_13) -> P(x_13). forall x_13: P_9(x_13) -> Q_9(x_13). forall x_13: P(x_13) -> T_1(x_13).
forall x_13: ~P_9(x_13) can be inferred via the universal modus tollens rule. exists x_13: P(x_13) -> Q_9(x_13) can be inferred via the existential transitivity rule. exists x_13: T_1(x_13) -> P_9(x_13) can be inferred via the existential transitivity rule. forall x_13: T_1(x_13) <-> P(x_13) can be inferred via the universal biconditional introduction rule. forall x_13: P(x_13) <-> T_1(x_13) can be inferred via the universal biconditional introduction rule.