(1) A cooperative library includes those areas consisting of 1 of the following:

    (a) Two or more counties with a total population of at least 100,000.

    (b) One county plus portions of other counties with a population of at least 100,000.

    (c) One county or portion of the county with a population of at least 400,000.

    (d) Portions of 2 or more counties with a population of at least 350,000.

    (e) Combinations of counties or portions of counties serving a population of at least 50,000, if the region served has a population of 35 or fewer persons per square mile.

    (2) The area covered by a cooperative library shall recognize the geosocioeconomic conditions within that area and regions established for governmental purposes throughout the state. A local board placed in a cooperative library may petition the department to be placed in a different cooperative library or to join with other local boards to form a cooperative library under this act. A local board serving an area adjoining more than 1 cooperative library may determine the cooperative library in which it participates.

    (3) The system board of an existing library system serving over 600,000 population may petition the department for designation as a cooperative board, and the department shall designate that system board, as already constituted, as the cooperative board. If a cooperative board is a county library board, the cooperative plan shall provide for expanding the cooperative board to represent proportionately the population served in any other county or counties within the area of the cooperative library. This expanded cooperative board shall have authority over those matters affecting the operation of the cooperative library except for the property, personnel, and governmental relationships of the county whose board was designated as the cooperative board, which matters shall continue to be the responsibility of that county library board. The department shall include in the cooperative library serving over 600,000 population the communities presently served by the existing system and all other communities not in another cooperative library within counties represented by members on the expanded cooperative board other than the designated system board members.