Consider the following premises. Sarah is not writing a letter. For all x_21, x_21 will write a letter or x_21 will play squash. James is not cooking. If Robert were a writer, then James is cooking. Can we infer the following from them? If we can, name the inference rule being used: Robert is a writer.
 From the fact that for all x_21, x_21 will write a letter or x_21 will play squash we can infer that Sarah is writing a letter or Sarah is playing squash via universal instantiation. From the fact that Sarah is writing a letter or Sarah is playing squash, and that Sarah is not writing a letter we can infer that Sarah is playing squash via disjunctive syllogism. Finally, from the fact that if Robert were a writer, then James is cooking, and that James is not cooking we can infer that Robert is not a writer via modus tollens, which contradicts that Robert is a writer. Therefore, the answer is no.