Consider the following premises. p_6 -> u_1. p_17 and q. u_1 -> p_6. u_1 -> ~p_17. Can we infer p_6 from them? If possible, name the inference rules being used at each step.
 From p_17 and q we can infer p_17 via simplification. From u_1 -> ~p_17, p_17 we can infer ~u_1 via modus tollens. From p_6 -> u_1, u_1 -> p_6 we can infer p_6 <-> u_1 via biconditional introduction. From p_6 <-> u_1 we can infer p_6 -> u_1 via biconditional elimination. Finally, from p_6 -> u_1, ~u_1 we can infer ~p_6 via modus tollens, which contradicts p_6. Therefore, the answer is no.