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: U(y_1) -> P_3(y_1). forall y_1: U(y_1) <-> P_3(y_1). exists y_1: P_3(y_1) -> U(y_1).
exists y_1: P_3(y_1) <-> U(y_1) can be inferred via the existential biconditional introduction rule. exists y_1: U(y_1) <-> P_3(y_1) can be inferred via the existential biconditional introduction rule. forall y_1: U(y_1) -> P_3(y_1) can be inferred via the universal biconditional elimination rule. forall y_1: P_3(y_1) -> U(y_1) can be inferred via the universal biconditional elimination rule.