Consider the following premises. q_6 -> s. t_2 -> q_6. s -> q_16. q_16 -> t_2. q_16 -> s. Can we infer t_2 <-> q_16 from them? If possible, name the inference rules being used at each step.
 From s -> q_16, q_16 -> s we can infer s <-> q_16 via biconditional introduction. From s <-> q_16 we can infer s -> q_16 via biconditional elimination. From t_2 -> q_6, q_6 -> s we can infer t_2 -> s via transitivity. From t_2 -> s, s -> q_16 we can infer t_2 -> q_16 via transitivity. Finally, from t_2 -> q_16, q_16 -> t_2 we can infer t_2 <-> q_16 via biconditional introduction. Therefore, the answer is yes.