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_1(y) -> T_3(y). forall y: T_3(y) -> U_1(y). forall y: T_3(y).
forall y: U_1(y) can be inferred via the universal modus ponens rule. forall y: U_1(y) <-> T_3(y) can be inferred via the universal biconditional introduction rule. forall y: T_3(y) <-> U_1(y) can be inferred via the universal biconditional introduction rule.