For a contract authorizing occupancy by the concessionaire for a period of more than three years of any portion of the state park system, the department shall prepare an invitation to bid, which shall include a summary of the terms and conditions of the concession sufficient to enable persons to bid solely on the basis of rates to be paid to the state. The invitation to bid shall specify the minimum acceptable rent,

except in instances in which a minimum acceptable rent cannot be ascertained because of the novelty or uniqueness of the service or facility to be provided or in instances in which the department has determined that a better return to the state can be secured by not specifying a minimum acceptable rent. Bids shall be made only on the basis of the invitation to bid.