Consider the following premises. ~s. r_2 -> t. t -> s. Can we infer ~r_2 or q from them? If possible, name the inference rules being used at each step.
 From t -> s, ~s we can infer ~t via modus tollens. From r_2 -> t, ~t we can infer ~r_2 via modus tollens. Finally, from ~r_2 we can infer ~r_2 or q via addition. Therefore, the answer is yes.