Consider the following premises. ~r_3. r_3 or s_4. t -> r_6. p_6 -> r_6. p_12 -> ~s_4. p_6 or t. Can we infer p_12 from them?
 From r_3 or s_4, ~r_3 we can infer s_4. Finally, from p_12 -> ~s_4, s_4 we can infer ~p_12, which contradicts p_12. Therefore, the answer is no.