Consider the following premises. There is at least one x_9 for which x_9 is a politician if and only if x_9 is a musician. For all x_9, x_9 is a politician if and only if x_9 is happy. Can we infer the following from them? There is at least one x_9 for which if x_9 were a musician, then x_9 is happy.
 From the fact that there is at least one x_9 for which x_9 is a politician if and only if x_9 is a musician we can infer that there is at least one x_9 for which if x_9 were a musician, then x_9 is a politician. From the fact that for all x_9, x_9 is a politician if and only if x_9 is happy we can infer that for all x_9, if x_9 were a politician, then x_9 is happy. Finally, from the fact that there is at least one x_9 for which if x_9 were a musician, then x_9 is a politician, and that for all x_9, if x_9 were a politician, then x_9 is happy we can infer that there is at least one x_9 for which if x_9 were a musician, then x_9 is happy. Therefore, the answer is yes.