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 z_1: ~S(z_1). forall z_1: S(z_1) or S_1(z_1). q_2 <-> q_18. ~q_2.
q_2 -> q_18 can be inferred via the biconditional elimination rule. q_18 -> q_2 can be inferred via the biconditional elimination rule. ~q_18 can be inferred via the biconditional elimination rule. forall z_1: S_1(z_1) can be inferred via the universal disjunctive syllogism rule.