(b) When a child is placed for adoption by a social services official or a voluntary authorized agency with adoptive parents residing in another social services district, the "board rate" shall mean the board rate of the social services district placing the child for adoption or the social services district in which the adoptive parents reside. 5. "Persons" shall include a single person eligible to adopt a child as well as a couple eligible therefor. 6. "Voluntary authorized agency" shall mean an authorized agency as defined in paragraphs (a) and (c) of subdivision ten of section three hundred seventy-one of this article. 7. "Social services official" shall mean a county commissioner of social services, a city commissioner of social services, or an Indian tribe with which the department has entered into an agreement to provide adoption services in accordance with subdivision two of section thirty-nine of this chapter.