At the meeting described in section 58-02-14, the members of the boards of township supervisors and the township clerks there present shall determine the value of the townhall and of all other property owned and used by the township to which the new territory has been annexed and the value of the property of the township or fraction of a township which has been annexed thereto, and shall compute the amount of moneys in the township treasury and of moneys due to the township to which the new territory has been annexed and to the township or fraction of a township annexed thereto, from the county and from other sources, and the amount of back or unpaid taxes due to the township to which the new territory has been annexed and due to and receivable by the township or fraction of a township annexed thereto, to determine the gross assets of the territories involved. They shall compute the amount of all bonds and debts which constitute the legal liabilities of the township to which the territory is annexed, and the difference between the gross assets and the liabilities constitutes the net assets or the net liabilities of such township for use in determining the pro rata amount, if any, due from the annexed territory.