Consider the following premises. There is at least one x_3 for which x_3 will play squash if and only if x_3 will sleep. For all x_3, x_3 will play squash or x_3 will not sleep. Can we infer the following from them? There is at least one x_3 for which if x_3 sleeps, then x_3 is playing squash.
 From the fact that for all x_3, x_3 will play squash or x_3 will not sleep we can infer that for all x_3, if x_3 sleeps, then x_3 is playing squash. From the fact that there is at least one x_3 for which x_3 will play squash if and only if x_3 will sleep we can infer that there is at least one x_3 for which if x_3 plays squash, then x_3 is sleeping. From the fact that for all x_3, if x_3 sleeps, then x_3 is playing squash, and that there is at least one x_3 for which if x_3 plays squash, then x_3 is sleeping we can infer that there is at least one x_3 for which x_3 will sleep if and only if x_3 will play squash. Finally, from the fact that there is at least one x_3 for which x_3 will sleep if and only if x_3 will play squash we can infer that there is at least one x_3 for which if x_3 sleeps, then x_3 is playing squash. Therefore, the answer is yes.