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_16: P_16(x_16) -> Q_3(x_16). exists x_16: Q_4(x_16). forall x_16: Q_3(x_16) -> ~Q_4(x_16). forall x_16: P_16(x_16) <-> R_3(x_16).
exists x_16: ~Q_3(x_16) can be inferred via the existential modus tollens rule. forall x_16: P_16(x_16) -> R_3(x_16) can be inferred via the universal biconditional elimination rule. forall x_16: R_3(x_16) -> P_16(x_16) can be inferred via the universal biconditional elimination rule.