Final answer:
Government Corporations perform a service for a fee within the bureaucracy. They generate enough profit to be self-sustaining, but they also fulfill a vital service that the government has an interest in maintaining.
Step-by-step explanation:
The part of the bureaucracy that performs a service for a fee is Government Corporations. These agencies are formed by the federal government to administer quasi-business enterprises that are partly subject to market forces. They generate enough profit to be self-sustaining, but they also fulfill a vital service that the government has an interest in maintaining. Government corporations, unlike private corporations, do not have stockholders and their profits are dedicated to perpetuating the enterprise.