Consider the following premises. For all x_20, x_20 will sleep or x_20 is a doctor. For all x_20, if x_20 were an artist, then x_20 is not a doctor. If it is overcast, then James is an artist. For all x_20, x_20 will not sleep. Can we infer the following from them? If we can, name the inference rule being used: It is not overcast or Richard is reading a book.
 From the fact that for all x_20, x_20 will sleep or x_20 is a doctor, and that for all x_20, x_20 will not sleep we can infer that for all x_20, x_20 is a doctor via universal disjunctive syllogism. From the fact that for all x_20, if x_20 were an artist, then x_20 is not a doctor, and that for all x_20, x_20 is a doctor we can infer that for all x_20, x_20 is not an artist via universal modus tollens. From the fact that for all x_20, x_20 is not an artist we can infer that James is not an artist via universal instantiation. From the fact that if it is overcast, then James is an artist, and that James is not an artist we can infer that it is not overcast via modus tollens. Finally, from the fact that it is not overcast we can infer that it is not overcast or Richard is reading a book via addition. Therefore, the answer is yes.