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 x_1: T_4(x_1) -> U(x_1). forall x_1: R_4(x_1) <-> S(x_1). forall x_1: ~R_4(x_1). forall x_1: U(x_1) -> T_4(x_1). forall x_1: T_4(x_1) <-> S(x_1).
exists x_1: T_4(x_1) <-> U(x_1) can be inferred via the existential biconditional introduction rule. exists x_1: U(x_1) <-> T_4(x_1) can be inferred via the existential biconditional introduction rule. forall x_1: R_4(x_1) -> S(x_1) can be inferred via the universal biconditional elimination rule. forall x_1: T_4(x_1) -> S(x_1) can be inferred via the universal biconditional elimination rule. forall x_1: S(x_1) -> R_4(x_1) can be inferred via the universal biconditional elimination rule. forall x_1: S(x_1) -> T_4(x_1) can be inferred via the universal biconditional elimination rule. forall x_1: ~S(x_1) can be inferred via the universal biconditional elimination rule.