Consider the following premises. ~s. q_2 or ~r_1. q_11 <-> q_2. s -> q_11. q_11 -> s. Can we infer r_1 from them?
 From q_2 or ~r_1 we can infer r_1 -> q_2. From s -> q_11, q_11 -> s we can infer s <-> q_11. From s <-> q_11, ~s we can infer ~q_11. From q_11 <-> q_2, ~q_11 we can infer ~q_2. Finally, from r_1 -> q_2, ~q_2 we can infer ~r_1, which contradicts r_1. Therefore, the answer is no.