What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? Name the inference rule being used: For all x_4, if x_4 were fast, then x_4 is sleeping. For all x_4, if x_4 were a server, then x_4 is writing a letter. There is at least one x_4 for which x_4 is not a poet or x_4 is fast. For all x_4, x_4 is a poet or x_4 is a server. For all x_4, if x_4 sleeps, then x_4 is writing a letter.
For all x_4, if x_4 were fast, then x_4 is writing a letter can be inferred via the universal transitivity rule. There is at least one x_4 for which x_4 is a server or x_4 is fast can be inferred via the existential resolution rule.