designates or establishes a single State agency, which may be an interdepartmental agency, as the sole agency for carrying out the purposes of this subchapter;

indicates the manner in which provision will be made to assure full consideration of all aspects of services essential to planning for comprehensive State and community action to combat mental retardation, including services in the fields of education, employment, rehabilitation, welfare, health, and the law, and services provided through community programs for and institutions for the mentally retarded;