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