Consider the following premises. For all x_6, x_6 will not write a letter. There is at least one x_6 for which x_6 is a police officer. For all x_6, x_6 will write a letter if and only if x_6 is a police officer. Can we infer the following from them? If we can, name the inference rule being used: For all x_6, x_6 is not a server.
The premises are contradictory and we can infer anything from them. Therefore, the answer is yes.