Consider the following premises. s_4 -> p_1. p_1 -> s_4. ~p_1. Can we infer s_4 from them?
 From p_1 -> s_4, s_4 -> p_1 we can infer p_1 <-> s_4. Finally, from p_1 <-> s_4, ~p_1 we can infer ~s_4, which contradicts s_4. Therefore, the answer is no.