Consider the following premises. p_10 <-> s. u -> r. s -> u. r -> s. ~p_10. Can we infer r from them?
 From p_10 <-> s, ~p_10 we can infer ~s. From s -> u, u -> r we can infer s -> r. From s -> r, r -> s we can infer s <-> r. Finally, from s <-> r, ~s we can infer ~r, which contradicts r. Therefore, the answer is no.