Consider the following premises. ~p_11 -> u. ~q_11. s_2. p_11 -> q_11. Can we infer s_2 and u from them? If possible, name the inference rules being used at each step.
 From p_11 -> q_11, ~q_11 we can infer ~p_11 via modus tollens. From ~p_11 -> u, ~p_11 we can infer u via modus ponens. Finally, from s_2, u we can infer s_2 and u via conjunction. Therefore, the answer is yes.