Consider the following premises. u <-> q_8. q_8 <-> w_1. ~p_1. u <-> p_1. Can we infer w_1 from them? If possible, name the inference rules being used at each step.
 From u <-> p_1, ~p_1 we can infer ~u via biconditional elimination. From u <-> q_8, ~u we can infer ~q_8 via biconditional elimination. From q_8 <-> w_1 we can infer w_1 -> q_8 via biconditional elimination. Finally, from w_1 -> q_8, ~q_8 we can infer ~w_1 via modus tollens, which contradicts w_1. Therefore, the answer is no.