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: s. ~U(a). s -> r_3. forall z_3: W(z_3) <-> U(z_3).
r_3 can be inferred via the modus ponens rule. s and ~U(a) can be inferred via the conjunction rule. ~U(a) and s can be inferred via the conjunction rule. forall z_3: W(z_3) -> U(z_3) can be inferred via the universal biconditional elimination rule. forall z_3: U(z_3) -> W(z_3) can be inferred via the universal biconditional elimination rule.