Funding or refunding bonds may be issued in a principal amount sufficient to provide funds for the payment of all bonds to be funded or refunded by such funding or refunding bonds, and in addition for the payment of all expenses incident to the calling, retiring, or paying of such outstanding bonds, and the issuance of such funding or refunding bonds. These expenses include the difference in amount between the par value of the funding or refunding bonds and any amount less than par for which the funding or refunding bonds are sold, any amount necessary to be made available for the payment of interest upon such funding or refunding bonds from the date of sale of the funding or refunding bonds to the date of payment of the bonds to be funded or refunded or to the date upon which the bonds to be funded or refunded will be paid pursuant to the call of the bonds to be funded or refunded or agreement with the holders of the bonds to be funded or refunded, and the premium, if any, necessary to be paid in order to call or retire the outstanding bonds and the interest accruing on the outstanding bonds to the date of the call or retirement.