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_8: P_5(x_8) <-> U_4(x_8). forall x_8: U(x_8) <-> U_4(x_8).
forall x_8: U(x_8) -> U_4(x_8) can be inferred via the universal biconditional elimination rule. exists x_8: P_5(x_8) -> U_4(x_8) can be inferred via the existential biconditional elimination rule. forall x_8: U_4(x_8) -> U(x_8) can be inferred via the universal biconditional elimination rule. exists x_8: U_4(x_8) -> P_5(x_8) can be inferred via the existential biconditional elimination rule.