Consider the following premises. For all x_7, x_7 will not sleep. For all x_7, x_7 will sleep. There is at least one x_7 for which x_7 will not play tennis. Can we infer the following from them? There is at least one x_7 for which x_7 is an office clerk.
 From the fact that for all x_7, x_7 will sleep we can infer that for all x_7, x_7 will sleep or x_7 will play tennis. From the fact that for all x_7, x_7 will sleep or x_7 will play tennis, and that for all x_7, x_7 will not sleep we can infer that for all x_7, x_7 will play tennis. From the fact that for all x_7, x_7 will play tennis we can infer that for all x_7, x_7 will play tennis or x_7 is an office clerk. Finally, from the fact that for all x_7, x_7 will play tennis or x_7 is an office clerk, and that there is at least one x_7 for which x_7 will not play tennis we can infer that there is at least one x_7 for which x_7 is an office clerk. Therefore, the answer is yes. Notice, however, that the premises were contradictory, so we can infer anything from them.