Consider the following premises. q_1 or ~u. q_1 <-> r. Can we infer u -> r from them? If possible, name the inference rules being used at each step.
 From q_1 <-> r we can infer q_1 -> r via biconditional elimination. From q_1 or ~u we can infer u -> q_1 via rewriting. Finally, from u -> q_1, q_1 -> r we can infer u -> r via transitivity. Therefore, the answer is yes.