Consider the following premises. There is at least one x_8 for which if x_8 were a nurse, then x_8 is sad. For all x_8, x_8 is a nurse if and only if x_8 is an office clerk. For all x_8, if x_8 were sad, then x_8 is an office clerk. Can we infer the following from them? There is at least one x_8 for which x_8 is sad if and only if x_8 is a nurse.
 From the fact that for all x_8, x_8 is a nurse if and only if x_8 is an office clerk we can infer that for all x_8, if x_8 were an office clerk, then x_8 is a nurse. From the fact that for all x_8, if x_8 were sad, then x_8 is an office clerk, and that for all x_8, if x_8 were an office clerk, then x_8 is a nurse we can infer that for all x_8, if x_8 were sad, then x_8 is a nurse. Finally, from the fact that for all x_8, if x_8 were sad, then x_8 is a nurse, and that there is at least one x_8 for which if x_8 were a nurse, then x_8 is sad we can infer that there is at least one x_8 for which x_8 is sad if and only if x_8 is a nurse. Therefore, the answer is yes.