Consider the following premises. For all x_5, x_5 is a janitor if and only if x_5 will go running. For all x_5, x_5 is not a doctor. There is at least one x_5 for which x_5 is a doctor if and only if x_5 will go running. Can we infer the following from them? There is at least one x_5 for which x_5 is not a janitor.
 From the fact that there is at least one x_5 for which x_5 is a doctor if and only if x_5 will go running, and that for all x_5, x_5 is not a doctor we can infer that there is at least one x_5 for which x_5 will not go running. Finally, from the fact that for all x_5, x_5 is a janitor if and only if x_5 will go running, and that there is at least one x_5 for which x_5 will not go running we can infer that there is at least one x_5 for which x_5 is not a janitor. Therefore, the answer is yes.