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 x_4: P(x_4) -> U_1(x_4). forall x_4: U_1(x_4) -> T(x_4). exists x_4: ~T(x_4). forall x_4: U_1(x_4) -> P(x_4).
exists x_4: ~U_1(x_4) can be inferred via the existential modus tollens rule. forall x_4: P(x_4) -> T(x_4) can be inferred via the universal transitivity rule. forall x_4: P(x_4) <-> U_1(x_4) can be inferred via the universal biconditional introduction rule. forall x_4: U_1(x_4) <-> P(x_4) can be inferred via the universal biconditional introduction rule.