Consider the following premises. For all x_2, if x_2 plays squash, then x_2 is a taxi driver. For all x_2, x_2 will play squash if and only if x_2 is sad. There is at least one x_2 for which x_2 is not a taxi driver. Can we infer the following from them? For all x_2, x_2 is sad.
 From the fact that for all x_2, if x_2 plays squash, then x_2 is a taxi driver, and that there is at least one x_2 for which x_2 is not a taxi driver we can infer that there is at least one x_2 for which x_2 will not play squash. Finally, from the fact that for all x_2, x_2 will play squash if and only if x_2 is sad, and that there is at least one x_2 for which x_2 will not play squash we can infer that there is at least one x_2 for which x_2 is not sad, which contradicts that For all x_2, x_2 is sad. Therefore, the answer is no.