When the amount in controversy in any action at law in a general district court does not exceed the sum of $2,500, exclusive of interest, attorney fees contracted for in the instrument, and costs, a corporate plaintiff or defendant, the stock of which is held by no more than five persons and is not publicly offered or planned to be publicly offered at the time of the litigation, may be represented by an officer of that corporation who shall have all the rights and privileges given an individual to represent, plead, and try a case without an attorney, provided that such officer has the unanimous consent of all the shareholders to do so.