The Board may, with the consent of the Governor, sell and issue refunding bonds of the Commonwealth to refund any or all of the Commonwealth’s bonds or other debt. The aggregate principal amount of such refunding bonds shall not exceed the amount required to redeem or otherwise provide for the payment of the unpaid principal of and interest on and any redemption premium payable on the bonds to be refunded to their date of redemption or payment, plus all expenses incurred in such refunding transaction.