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