A yellow pages server maintains a table of Benefits indexed by the providers who provide them:
| Benefit | Providers | 
| Dental | Delta, BlueShield | 
| Psychiatric | BlueCross,  | 
| Surgical | BlueCross,
  BlueShield,  | 
Implement the YellowPages server first as a singleton class, then again as a utility class.
Create a test harness for your implementations.