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: U_4(y) -> T(y). forall y: T(y) or T_1(y). exists y: T_1(y) -> U_4(y). forall y: T(y) -> U_4(y).
exists y: T_1(y) -> T(y) can be inferred via the existential transitivity rule. exists y: U_4(y) can be inferred via the existential disjunction elimination rule. forall y: U_4(y) <-> T(y) can be inferred via the universal biconditional introduction rule. forall y: T(y) <-> U_4(y) can be inferred via the universal biconditional introduction rule.