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_15: W(x_15) <-> R(x_15). forall x_15: ~P(x_15). forall x_15: R(x_15) -> P(x_15). forall x_15: R(x_15) <-> W(x_15).
forall x_15: ~R(x_15) can be inferred via the universal modus tollens rule. forall x_15: R(x_15) -> W(x_15) can be inferred via the universal biconditional elimination rule. exists x_15: W(x_15) -> R(x_15) can be inferred via the existential biconditional elimination rule. forall x_15: W(x_15) -> R(x_15) can be inferred via the universal biconditional elimination rule. exists x_15: R(x_15) -> W(x_15) can be inferred via the existential biconditional elimination rule.