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_6, x_6 is a server or x_6 will write a letter. For all x_6, x_6 is rich or x_6 will not write a letter. For all x_6, if x_6 were a server, then x_6 is rich.
For all x_6, if x_6 writes a letter, then x_6 is rich can be inferred via the universal rewriting rule.