(d) The governing body of the city may agree to assume any or all of the outstanding debt and other liabilities of the district. The governing body of the city may issue general obligation bonds of such city to acquire the sewerage system and pay the outstanding debt and liabilities assumed thereby when acquiring such sewerage system. All costs incurred by the city pursuant to an agreement authorized by subsection (b) may be paid by the city at large or from the general improvement fund, general revenue fund, internal improvement fund, or any other fund or funds of such city which are available for such purposes.