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 y_1: ~P(y_1). exists y_1: U(y_1) <-> P_3(y_1). forall y_1: P_3(y_1) or S(y_1). forall y_1: U(y_1) -> P(y_1).
forall y_1: ~U(y_1) can be inferred via the universal modus tollens rule. exists y_1: U(y_1) -> P_3(y_1) can be inferred via the existential biconditional elimination rule. exists y_1: P_3(y_1) -> U(y_1) can be inferred via the existential biconditional elimination rule.