Consider the following premises. p_12 <-> r_3. u or p_12. u -> r_3. p_4. Can we infer r_3 and p_4 from them?
 From p_12 <-> r_3 we can infer p_12 -> r_3. From u -> r_3, p_12 -> r_3, u or p_12 we can infer r_3. Finally, from r_3, p_4 we can infer r_3 and p_4. Therefore, the answer is yes.