Consider the following premises. There is at least one x_15 for which x_15 will work if and only if x_15 is poor. For all x_15, x_15 is poor if and only if x_15 will work. For all x_15, x_15 is not happy. For all x_15, if x_15 were poor, then x_15 is happy. Can we infer the following from them? There is at least one x_15 for which x_15 will not work.
 From the fact that there is at least one x_15 for which x_15 will work if and only if x_15 is poor we can infer that there is at least one x_15 for which if x_15 were poor, then x_15 is working. From the fact that for all x_15, x_15 is poor if and only if x_15 will work we can infer that for all x_15, if x_15 works, then x_15 is poor. From the fact that for all x_15, if x_15 works, then x_15 is poor, and that there is at least one x_15 for which if x_15 were poor, then x_15 is working we can infer that there is at least one x_15 for which x_15 will work if and only if x_15 is poor. From the fact that for all x_15, if x_15 were poor, then x_15 is happy, and that for all x_15, x_15 is not happy we can infer that for all x_15, x_15 is not poor. Finally, from the fact that there is at least one x_15 for which x_15 will work if and only if x_15 is poor, and that for all x_15, x_15 is not poor we can infer that there is at least one x_15 for which x_15 will not work. Therefore, the answer is yes.