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: u <-> q. s. q or q_4. ~u.
s and ~u can be inferred via the conjunction rule. ~u and s can be inferred via the conjunction rule. u -> q can be inferred via the biconditional elimination rule. q -> u can be inferred via the biconditional elimination rule. ~q can be inferred via the biconditional elimination rule.