Consider the following premises. p_3 -> u_3. u_3 -> t. t -> u_3. t -> q. q -> p_3. Can we infer q <-> t from them?
 From u_3 -> t, t -> u_3 we can infer u_3 <-> t. From u_3 <-> t we can infer u_3 -> t. From q -> p_3, p_3 -> u_3 we can infer q -> u_3. From q -> u_3, u_3 -> t we can infer q -> t. Finally, from q -> t, t -> q we can infer q <-> t. Therefore, the answer is yes.