4. An excerpt from the prospectus of a $200 million issue by Becton, Dickinson and Company 7.15% Notes due October 1, 2009: OPTIONAL REDEMPTION We may, at our option, redeem all or any part of the notes. If we choose to do so, we will mail a notice of redemption to you not less than 30 days and not more than 60 days before this redemption occurs. The redemption price will be equal to the greater of: (1) 100% of the principal amount of the notes to be redeemed; and (2) the sum of the present values of the Remaining Scheduled Payments on the notes, discounted to the redemption date on a semiannual basis, assuming a 360-day year consisting of twelve 30-day months, at the Treasury Rate plus 15 basis points. a. What type of call provision is this? b. What is the purpose of this type of call provision