The board is hereby empowered to issue refunding bonds to provide funds to refund any or all outstanding bonds payable from the bond retirement fund and to pay any redemption premium payable on such outstanding bonds being refunded. Such refunding bonds may be issued in the manner and on terms and conditions and with the covenants permitted by this chapter for the issuance of bonds. The refunding bonds shall be payable out of the bond retirement fund and shall not constitute an obligation either general or special, of the state or a general obligation of the University of Washington or the board. The board may exchange the refunding bonds at par for the bonds which are being refunded or may sell them in such manner, at such price and at such rate or rates of interest as it deems for the best interest of the university.