namespace Utility {
  export namespace Fees {
    export function CalculateLateFees(daysLate: number): number {
      return daysLate * 0.25;
    }
  }

  export function MaxBooksAllowed(age: number): number {
    if (age < 12) {
      return 3;
    }
    else {
      return 10;
    }
  }

  // Since it is not exported, it will be private to the namespace.
  function privateFunc(): void {
    console.log('This is private...');
  }
}