Consider the following premises. t <-> w. p_6 or w. p_6 -> p. p -> t. Can we infer ~t from them?
 From p_6 -> p, p -> t we can infer p_6 -> t. From t <-> w we can infer w -> t. Finally, from p_6 -> t, w -> t, p_6 or w we can infer t, which contradicts ~t. Therefore, the answer is no.