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_2 or ~r. q -> r. t_2 <-> q.
r -> t_2 can be inferred via the rewriting rule. t_2 -> q can be inferred via the biconditional elimination rule. q -> t_2 can be inferred via the biconditional elimination rule.