Consider the following premises. p_7 or ~r. r <-> s_4. p_1 -> s_4. Can we infer p_1 -> p_7 from them?
 From r <-> s_4 we can infer s_4 -> r. From p_7 or ~r we can infer r -> p_7. From p_1 -> s_4, s_4 -> r we can infer p_1 -> r. Finally, from p_1 -> r, r -> p_7 we can infer p_1 -> p_7. Therefore, the answer is yes.