Consider the following premises. For all x_8, if x_8 writes a letter, then x_8 is a scientist. For all x_8, if x_8 reads a book, then x_8 is sad. For all x_8, if x_8 were sad, then x_8 is writing a letter. For all x_8, if x_8 were a scientist, then x_8 is reading a book. Can we infer the following from them? If Charles reads a book, then Charles is writing a letter.
 From the fact that for all x_8, if x_8 reads a book, then x_8 is sad, and that for all x_8, if x_8 were sad, then x_8 is writing a letter we can infer that for all x_8, if x_8 reads a book, then x_8 is writing a letter. From the fact that for all x_8, if x_8 writes a letter, then x_8 is a scientist, and that for all x_8, if x_8 were a scientist, then x_8 is reading a book we can infer that for all x_8, if x_8 writes a letter, then x_8 is reading a book. From the fact that for all x_8, if x_8 reads a book, then x_8 is writing a letter, and that for all x_8, if x_8 writes a letter, then x_8 is reading a book we can infer that for all x_8, x_8 will read a book if and only if x_8 will write a letter. From the fact that for all x_8, x_8 will read a book if and only if x_8 will write a letter we can infer that Charles is reading a book if and only if Charles is writing a letter. Finally, from the fact that Charles is reading a book if and only if Charles is writing a letter we can infer that if Charles reads a book, then Charles is writing a letter. Therefore, the answer is yes.