Consider the following premises. u. u <-> s_4. q_20 -> s_4. s -> ~s_4. p -> s. Can we infer ~p from them?
 From u we can infer u or q_20. From u <-> s_4 we can infer u -> s_4. From u -> s_4, q_20 -> s_4, u or q_20 we can infer s_4. From s -> ~s_4, s_4 we can infer ~s. Finally, from p -> s, ~s we can infer ~p. Therefore, the answer is yes.