Consider the following premises. p_6 -> s_4. t_2 -> q_11. p_6 or q_6. ~q_11. q_6 -> s_4. Can we infer ~s_4 from them?
 From t_2 -> q_11, ~q_11 we can infer ~t_2. Finally, from p_6 -> s_4, q_6 -> s_4, p_6 or q_6 we can infer s_4, which contradicts ~s_4. Therefore, the answer is no.