What is the duration of the following default-free bond portfolio? (4 dps) Note: Each bond has a face value of $1.00 and coupons are paid semi-annually. You should assume the zero-coupon rate calculated in part a above. Note: Use the following formula to measure the duration of the bond portfolio, i.e., DB=i=1ncieritii=1nticieriti, where ti,ci, and ri denote for term, cash-flows, and zero-coupon yield for the ith period. What is the duration of the following default-free bond portfolio? (4 dps) Note: Each bond has a face value of $1.00 and coupons are paid semi-annually. You should assume the zero-coupon rate calculated in part a above. Note: Use the following formula to measure the duration of the bond portfolio, i.e., DB=i=1ncieritii=1nticieriti, where ti,ci, and ri denote for term, cash-flows, and zero-coupon yield for the ith period