.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