The general manager shall furnish the board with an estimate of the tolls necessary to pay the obligations of the district. The board shall, upon the recommendation of the general manager, or such modifications thereof as it may adopt, fix such tolls as will:
(a)
First, pay the operating expenses of the district.
(b)
Second, provide for repairs and maintenance of works owned or operated by the district, including any payments to be made into a replacement fund for buses and ferries.
(c)
Third, provide for the purchase, lease, or other acquisition of district equipment, supplies, and other properties, including provision for interest, sinking funds, reserve funds, or other funds required for the payment of any obligations incurred by the district for the acquisition of such properties.
(d)
Fourth, pay any indebtedness or lien that may exist against the district or any of its property or revenues.