Sec. 4. (a) If a township or part of a township is contracting with a library that is extending service through a county contractual library, the township or part of a township:
(1) shall cease to levy a separate tax for library purposes; and
(2) becomes a part of the county contractual library district.
(b) The tax levy for county contractual library purposes shall then be levied in the township or part of a township that has become part of the county contractual library district.
(c) A township that ceases to levy a tax for public library purposes in any year becomes a part of the township's county library district or county contractual library district, if either library district exists at the time the township levy is discontinued. The county library or county contractual library tax shall then be levied in the townships.