When a fraction of a township has been detached from one organized township and attached to another, the detached territory shall assume and pay a just proportion of the indebtedness of the township from which it has been detached, based upon the last assessed valuation of the original civil township and in the proportion that the valuation of the detached portion bears to the valuation within the whole of the township from which it has been detached. At the meeting described in section 58-02-14, the members of the boards of township supervisors and the township clerks there present shall ascertain, as near as may be, the total outstanding indebtedness of the original township, as of the date upon which the detachment    became effective, and the amount of township assets which shall remain with the original township after the detachment, and the amount of the assets which must be paid over to the detached portion of such township and to the civil township to which such detached territory has been attached. Such determination must be based upon the last assessed valuation of the original township as provided in this section.