Consider the following premises. For all x_11, x_11 is not rich. There is at least one x_11 for which if x_11 were sad, then x_11 is working. For all x_11, x_11 is rich or x_11 is sad. Can we infer the following from them? If we can, name the inference rule being used: For all x_11, neither x_11 will work nor x_11 will write a letter.
That contradicts the premises. Therefore the answer is no.