When a landlord purchases utility services for residents, he shall provide residents with a monthly itemized bill that includes:
A. a separate listing of charges for each utility service;
B. the amount consumed and the cost per unit for each utility service; provided, that when individual cost per unit figures for utility services are not available, the landlord shall provide residents with the total cost of utility services and the formula used to determine the individual charges for utility services; and
C. if applicable, the amount of the administrative fee for providing utility services to residents.