Consider the following premises. ~q_4. p_7 <-> w_1. s -> q_4. ~p_7. Can we infer w_1 from them?
 From s -> q_4, ~q_4 we can infer ~s. Finally, from p_7 <-> w_1, ~p_7 we can infer ~w_1, which contradicts w_1. Therefore, the answer is no.