annual maturities as of december 31 , 2006 are scheduled as follows: .
what amount of interest expense was avoided per year by switching the 201c4.50% ( 201c4.50 % ) notes 201d with the 201c4.25% ( 201c4.25 % ) notes 201d?
1 in addition , holders of our $ 400.0 4.50% ( 4.50 % ) notes may require us to repurchase their 4.50% ( 4.50 % ) notes for cash at par in march 2008 . these notes will mature in 2023 if not converted or repurchased . redemption of long-term debt in august 2005 , we redeemed the remainder of our 7.875% ( 7.875 % ) senior unsecured notes with an aggregate principal amount of $ 250.0 at maturity for a total cost of $ 258.6 , which included the principal amount of the notes , accrued interest to the redemption date , and a prepayment penalty of $ 1.4 . to redeem these notes we used the proceeds from the sale and issuance in july 2005 of $ 250.0 floating rate senior unsecured notes due 2008 . floating rate senior unsecured notes in december 2006 , we exchanged all of our $ 250.0 floating rate notes due 2008 for $ 250.0 aggregate principal amount floating rate notes due 2010 . the new floating rate notes mature on november 15 , 2010 and bear interest at a per annum rate equal to three-month libor plus 200 basis points , 125 basis points less than the interest rate on the old floating rate notes . in connection with the exchange , we made an early participation payment of $ 41.25 ( actual amount ) in cash per $ 1000 ( actual amount ) principal amount of old floating rate notes for a total payment of $ 10.3 . in accordance with eitf issue no . 96-19 , debtor 2019s accounting for a modification or exchange of debt instruments ( 201ceitf 96-19 201d ) , this transaction is treated as an exchange of debt for accounting purposes because the present value of the remaining cash flows under the terms of the original instrument are not substantially different from those of the new instrument . the new floating rate notes are reflected on our consolidated balance sheet net of the $ 10.3 early participation payment , which is amortized over the life of the new floating rate notes as a discount , using an effective interest method , and recorded in interest expense . direct fees associated with the exchange of $ 3.5 were reflected in interest expense . 4.25% ( 4.25 % ) and 4.50% ( 4.50 % ) convertible senior notes in november 2006 , we exchanged $ 400.0 of our 4.50% ( 4.50 % ) convertible senior notes due 2023 ( the 201c4.50% ( 201c4.50 % ) notes 201d ) for $ 400.0 aggregate principal amount of 4.25% ( 4.25 % ) convertible senior notes due 2023 ( the 201c4.25% ( 201c4.25 % ) notes 201d ) . as required by eitf 96-19 , this exchange is treated as an extinguishment of the 4.50% ( 4.50 % ) notes and an issuance of 4.25% ( 4.25 % ) notes for accounting purposes because the present value of the remaining cash flows plus the fair value of the embedded conversion option under the terms of the original instrument are substantially different from those of the new instrument . as a result , the 4.25% ( 4.25 % ) notes are reflected on our consolidated balance sheet at their fair value at issuance , or $ 477.0 . we recorded a non-cash charge in the fourth quarter of 2006 of $ 77.0 reflecting the difference between the fair value of the new debt and the carrying value of the old debt . the difference between fair value and carrying value will be amortized through march 15 , 2012 , which is the first date holders may require us to repurchase the 4.25% ( 4.25 % ) notes , resulting in a reduction of reported interest expense in future periods . we also recorded a non-cash charge of $ 3.8 for the extinguishment of unamortized debt issuance costs related to the exchanged 4.50% ( 4.50 % ) notes . our 4.25% ( 4.25 % ) notes are convertible into our common stock at a conversion price of $ 12.42 per share , subject to adjustment in specified circumstances including any payment of cash dividends on our common stock . the conversion rate of the new notes is also subject to adjustment for certain events arising from stock splits and combinations , stock dividends , certain cash dividends and certain other actions by us that modify our capital notes to consolidated financial statements 2014 ( continued ) ( amounts in millions , except per share amounts ) %%transmsg*** transmitting job : y31000 pcn : 072000000 ***%%pcmsg|72 |00009|yes|no|02/28/2007 01:12|0|0|page is valid , no graphics -- color : d| .