Consider the following premises. w_3 -> q_4. p -> w_3. q_4 -> r_6. r_6 -> p. Can we infer p <-> r_6 from them?
 From w_3 -> q_4, q_4 -> r_6 we can infer w_3 -> r_6. From p -> w_3, w_3 -> r_6 we can infer p -> r_6. Finally, from p -> r_6, r_6 -> p we can infer p <-> r_6. Therefore, the answer is yes.