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: q_2. u_2 -> ~q_2. u_2 <-> q.
~u_2 can be inferred via the modus tollens rule. u_2 -> q can be inferred via the biconditional elimination rule. q -> u_2 can be inferred via the biconditional elimination rule.