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: R(a) <-> t. forall x_12: P_12(x_12) <-> U_3(x_12). forall x_12: U_3(x_12) <-> R(x_12). forall x_12: ~P_12(x_12).
R(a) -> t can be inferred via the biconditional elimination rule. t -> R(a) can be inferred via the biconditional elimination rule. forall x_12: P_12(x_12) -> U_3(x_12) can be inferred via the universal biconditional elimination rule. forall x_12: U_3(x_12) -> R(x_12) can be inferred via the universal biconditional elimination rule. forall x_12: U_3(x_12) -> P_12(x_12) can be inferred via the universal biconditional elimination rule. forall x_12: R(x_12) -> U_3(x_12) can be inferred via the universal biconditional elimination rule. forall x_12: ~U_3(x_12) can be inferred via the universal biconditional elimination rule.