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, x_4 is a doctor or x_4 is not a server. For all x_4, x_4 is a server or x_4 is not a doctor.
For all x_4, if x_4 were a server, then x_4 is a doctor can be inferred via the universal rewriting rule. For all x_4, if x_4 were a doctor, then x_4 is a server can be inferred via the universal rewriting rule.