8. Given the following information, use the approximation method to calculate the duration of the semiannual, option-free bond. (Use yield changes of 10 basis points to calculate P+ and P-, and carry price calculations to 3 digits.) Coupon: 6%, Initial Yield: 5%, Maturity: 10 yrs, Initial Price = 107.795 (per $100 par) a) 6.45 b) 7.57 c) 8.32 d) 4.57