Consider the following premises. s -> q_11. q_11 -> p_11. p_11 -> q_11. p_11 -> s. Can we infer s <-> p_11 from them? If possible, name the inference rules being used at each step.
 From p_11 -> q_11, q_11 -> p_11 we can infer p_11 <-> q_11 via biconditional introduction. From p_11 <-> q_11 we can infer q_11 -> p_11 via biconditional elimination. From s -> q_11, q_11 -> p_11 we can infer s -> p_11 via transitivity. Finally, from s -> p_11, p_11 -> s we can infer s <-> p_11 via biconditional introduction. Therefore, the answer is yes.