The State agency shall have as its primary function the administration of State labor laws and shall be under the direction of an executive who gives full time to the work of the agency. The agency shall be engaged in inspecting places of employment for (a) enforcement of State child-labor laws and regulations, and (b) enforcement of State maximum hour or minimum-wage laws and regulations. An administrative division of the State agency shall be designated to make investigations and inspections under the Acts; qualified staff, under adequate supervision, shall be specifically assigned for work connected with State and Federal child-labor, maximum-hour and minimum-wage laws and regulations; and provision shall be made to inspect any establishment subject to the Acts.