Consider the following premises. r_13 -> r_8. u -> r_13. p <-> r_8. p -> u. Can we infer p -> r_8 from them? If possible, name the inference rules being used at each step.
 From p -> u, u -> r_13 we can infer p -> r_13 via transitivity. Finally, from p -> r_13, r_13 -> r_8 we can infer p -> r_8 via transitivity. Therefore, the answer is yes.