Consider the following premises. For all x_12, x_12 is happy if and only if x_12 is a politician. For all x_12, if x_12 were a politician, then x_12 is not curious. For all x_12, x_12 will write a letter or x_12 will read a book. For all x_12, if x_12 writes a letter, then x_12 is curious. For all x_12, if x_12 reads a book, then x_12 is curious. Can we infer the following from them? There is at least one x_12 for which x_12 is happy.
 From the fact that for all x_12, if x_12 writes a letter, then x_12 is curious, that for all x_12, if x_12 reads a book, then x_12 is curious, and that for all x_12, x_12 will write a letter or x_12 will read a book we can infer that for all x_12, x_12 is curious. From the fact that for all x_12, x_12 is happy if and only if x_12 is a politician we can infer that for all x_12, if x_12 were happy, then x_12 is a politician. From the fact that for all x_12, if x_12 were a politician, then x_12 is not curious, and that for all x_12, x_12 is curious we can infer that for all x_12, x_12 is not a politician. Finally, from the fact that for all x_12, if x_12 were happy, then x_12 is a politician, and that for all x_12, x_12 is not a politician we can infer that for all x_12, x_12 is not happy, which contradicts that There is at least one x_12 for which x_12 is happy. Therefore, the answer is no.