Consider the following premises. For all x_7, x_7 will not sleep. For all x_7, x_7 will sleep if and only if x_7 is a taxi driver. For all x_7, x_7 is a taxi driver or x_7 is not fast. Can we infer the following from them? For all x_7, x_7 is not fast.
 From the fact that for all x_7, x_7 will sleep if and only if x_7 is a taxi driver, and that for all x_7, x_7 will not sleep we can infer that for all x_7, x_7 is not a taxi driver. From the fact that for all x_7, x_7 is a taxi driver or x_7 is not fast we can infer that for all x_7, if x_7 were fast, then x_7 is a taxi driver. Finally, from the fact that for all x_7, if x_7 were fast, then x_7 is a taxi driver, and that for all x_7, x_7 is not a taxi driver we can infer that for all x_7, x_7 is not fast. Therefore, the answer is yes.