Consider the following premises. For all x_10, if x_10 were a writer, then x_10 is a sailor. Karen is a writer if and only if John is a janitor. Can we infer the following from them? If John were a janitor, then Karen is a sailor.
 From the fact that for all x_10, if x_10 were a writer, then x_10 is a sailor we can infer that if Karen were a writer, then Karen is a sailor. From the fact that Karen is a writer if and only if John is a janitor we can infer that if John were a janitor, then Karen is a writer. Finally, from the fact that if John were a janitor, then Karen is a writer, and that if Karen were a writer, then Karen is a sailor we can infer that if John were a janitor, then Karen is a sailor. Therefore, the answer is yes.