Consider the following premises. There is at least one x_13 for which x_13 will sleep. For all x_13, x_13 is a server if and only if x_13 will sleep. Can we infer the following from them? If we can, name the inference rule being used: For all x_13, x_13 is a server if and only if x_13 will sleep.
That is one of the premises. Therefore, the answer is yes.