Consider the following premises. If David were a janitor, then Michael is reading a book. David is working or Michael is not reading a book. For all x_15, if x_15 works, then x_15 is a janitor. Can we infer the following from them? If is not true that Michael is reading a book if and only if David is working.
 From the fact that for all x_15, if x_15 works, then x_15 is a janitor we can infer that if David works, then David is a janitor. From the fact that if David works, then David is a janitor, and that if David were a janitor, then Michael is reading a book we can infer that if David works, then Michael is reading a book. From the fact that David is working or Michael is not reading a book we can infer that if Michael reads a book, then David is working. Finally, from the fact that if Michael reads a book, then David is working, and that if David works, then Michael is reading a book we can infer that Michael is reading a book if and only if David is working, which contradicts that If is not true that Michael is reading a book if and only if David is working. Therefore, the answer is no.