Consider the following premises. s -> p_8. ~p. p_8 -> s. p -> p_8. p_8 -> p. Can we infer ~s from them? If possible, name the inference rules being used at each step.
 From p_8 -> p, p -> p_8 we can infer p_8 <-> p via biconditional introduction. From s -> p_8, p_8 -> s we can infer s <-> p_8 via biconditional introduction. From p_8 <-> p, ~p we can infer ~p_8 via biconditional elimination. Finally, from s <-> p_8, ~p_8 we can infer ~s via biconditional elimination. Therefore, the answer is yes.