Consider the following premises. For all x_6, if x_6 were happy, then x_6 is fast. For all x_6, x_6 is happy if and only if x_6 is a nurse. For all x_6, if x_6 were fast, then x_6 is a nurse. Can we infer the following from them? There is at least one x_6 for which the fact that x_6 were a nurse does not imply that x_6 is happy.
 From the fact that for all x_6, if x_6 were happy, then x_6 is fast, and that for all x_6, if x_6 were fast, then x_6 is a nurse we can infer that for all x_6, if x_6 were happy, then x_6 is a nurse. From the fact that for all x_6, x_6 is happy if and only if x_6 is a nurse we can infer that for all x_6, if x_6 were a nurse, then x_6 is happy. From the fact that for all x_6, if x_6 were a nurse, then x_6 is happy, and that for all x_6, if x_6 were happy, then x_6 is a nurse we can infer that for all x_6, x_6 is a nurse if and only if x_6 is happy. Finally, from the fact that for all x_6, x_6 is a nurse if and only if x_6 is happy we can infer that for all x_6, if x_6 were a nurse, then x_6 is happy, which contradicts that There is at least one x_6 for which the fact that x_6 were a nurse does not imply that x_6 is happy. Therefore, the answer is no.