A. Any class B county of the state having a population of more than ninety-eight thousand but less than one hundred thousand, according to the last federal decennial census, and having a net taxable value for rate-setting purposes for the 1991 property tax year of more than one billion four hundred million dollars ($1,400,000,000) but less than one billion five hundred million dollars ($1,500,000,000) shall be permitted to purchase, own, operate and sell sewer and water utilities. Such class B counties shall not purchase, own, operate or sell any other utilities.

B. In the operation of a sewer or water utility by a class B county, the county shall set just and reasonable rates based on cost of service.