Consider the following premises. There is at least one x_4 for which if x_4 plays squash, then x_4 is taking a plane. For all x_4, x_4 is sad. For all x_4, if x_4 plays squash, then x_4 is not sad. For all x_4, if x_4 takes a plane, then x_4 is playing squash. Can we infer the following from them? For all x_4, x_4 will take a plane.
 From the fact that for all x_4, if x_4 plays squash, then x_4 is not sad, and that for all x_4, x_4 is sad we can infer that for all x_4, x_4 will not play squash. From the fact that for all x_4, if x_4 takes a plane, then x_4 is playing squash, and that there is at least one x_4 for which if x_4 plays squash, then x_4 is taking a plane we can infer that there is at least one x_4 for which x_4 will take a plane if and only if x_4 will play squash. Finally, from the fact that there is at least one x_4 for which x_4 will take a plane if and only if x_4 will play squash, and that for all x_4, x_4 will not play squash we can infer that there is at least one x_4 for which x_4 will not take a plane, which contradicts that For all x_4, x_4 will take a plane. Therefore, the answer is no.