Consider the following premises. s_3 -> r. p_11 -> s_3. r -> w_2. w_2 -> u. p_6 -> p_11. Can we infer p_6 -> u from them? If possible, name the inference rules being used at each step.
 From p_11 -> s_3, s_3 -> r we can infer p_11 -> r via transitivity. From p_6 -> p_11, p_11 -> r we can infer p_6 -> r via transitivity. From r -> w_2, w_2 -> u we can infer r -> u via transitivity. Finally, from p_6 -> r, r -> u we can infer p_6 -> u via transitivity. Therefore, the answer is yes.