(a) A related organization shall be defined as any entity which the residential treatment facility is in control of or is controlled by, either directly or indirectly, or where an association of material interest exists in an entity which supplies goods and/or services to the residential treatment facility, or any entity which is controlled directly or indirectly by the immediate family of the provider of services. Immediate family shall include each parent, child, spouse, brother, sister, first cousin, aunt and uncle, whether such relationship arises by reason of birth, marriage or adoption.

(b) The costs of goods and/or services furnished to a residential treatment facility by a related organization are includable in the computation of the basic rate of payment at the lower of the cost to the related organization or the market price of comparable goods and/or services available in the residential treatment facility within the course of normal business operations.