Consider the following premises. p -> w_1. u_4 -> w_1. w_1 -> p. p or u_4. Can we infer w_1 from them?
 From p -> w_1, w_1 -> p we can infer p <-> w_1. From p <-> w_1 we can infer p -> w_1. Finally, from p -> w_1, u_4 -> w_1, p or u_4 we can infer w_1. Therefore, the answer is yes.