Consider the following premises. q_4 or ~u. q_4 -> q_1. q_1 -> t_2. Can we infer u -> t_2 from them? If possible, name the inference rules being used at each step.
 From q_4 or ~u we can infer u -> q_4 via rewriting. From q_4 -> q_1, q_1 -> t_2 we can infer q_4 -> t_2 via transitivity. Finally, from u -> q_4, q_4 -> t_2 we can infer u -> t_2 via transitivity. Therefore, the answer is yes.