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 y: U_4(y) -> P_2(y). forall y: W(y) -> P_2(y). forall y: P_2(y) -> U_4(y). forall y: W(y) or U_4(y).
forall y: W(y) -> U_4(y) can be inferred via the universal transitivity rule. exists y: P_2(y) can be inferred via the existential disjunction elimination rule. exists y: U_4(y) <-> P_2(y) can be inferred via the existential biconditional introduction rule. exists y: P_2(y) <-> U_4(y) can be inferred via the existential biconditional introduction rule.