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_17: P_17(x_17) or Q_17(x_17). forall x_17: P_4(x_17) or P_7(x_17). forall x_17: P_4(x_17) -> Q_7(x_17). forall x_17: Q_17(x_17) -> S(x_17). forall x_17: P_7(x_17) <-> Q_7(x_17). forall x_17: P_17(x_17) -> S(x_17).
exists x_17: S(x_17) can be inferred via the existential disjunction elimination rule. forall x_17: P_7(x_17) -> Q_7(x_17) can be inferred via the universal biconditional elimination rule. forall x_17: Q_7(x_17) -> P_7(x_17) can be inferred via the universal biconditional elimination rule.