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: t <-> q_2. q_2 or ~s.
s -> q_2 can be inferred via the rewriting rule. t -> q_2 can be inferred via the biconditional elimination rule. q_2 -> t can be inferred via the biconditional elimination rule.