Consider the following premises. p_8 -> s. s -> q_1. q_1 -> p_8. p_8 -> q_1. Can we infer p_8 <-> q_1 from them? If possible, name the inference rules being used at each step.
 From p_8 -> s, s -> q_1 we can infer p_8 -> q_1 via transitivity. From q_1 -> p_8, p_8 -> q_1 we can infer q_1 <-> p_8 via biconditional introduction. From q_1 <-> p_8 we can infer q_1 -> p_8 via biconditional elimination. Finally, from p_8 -> q_1, q_1 -> p_8 we can infer p_8 <-> q_1 via biconditional introduction. Therefore, the answer is yes.