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: U(x) -> R(x). forall x: R(x) -> U(x). forall x: U(x) -> R(x).
forall x: U(x) <-> R(x) can be inferred via the universal biconditional introduction rule. forall x: R(x) <-> U(x) can be inferred via the universal biconditional introduction rule. forall x: R(x) <-> U(x) can be inferred via the universal biconditional introduction rule. forall x: U(x) <-> R(x) can be inferred via the universal biconditional introduction rule.