Consider the following premises. p_7 or q_7. ~p_7 or u. u <-> r. q_7 -> r. Can we infer ~r from them? If possible, name the inference rules being used at each step.
 From p_7 or q_7, ~p_7 or u we can infer q_7 or u via resolution. From u <-> r we can infer u -> r via biconditional elimination. Finally, from q_7 -> r, u -> r, q_7 or u we can infer r via disjunction elimination, which contradicts ~r. Therefore, the answer is no.