Give me the detail process,how can I calculate the P0,P+ and P-

Step1: Increase the yield on the bond by a small number of basis points and determine the new price at this higher yield level. We denote this new price by P Step 2: Decrease the yield on the bond by the same number of basis points and calculate the new price. We will denote this new price by P Step 3: Letting P, be the initial price, duration can be approximated using the following formula: P-P+ approximate duration 2(P,)(Ay) 4.23) To see how good this approximation is, let's apply it to the 25-year 6% coupon bond trading at 9%. All the necessary information is provided in Exhibit 4-2. The initial price (P) is 70.3570. The steps are as follows: Increase the yield on the bond by 10 basis points from 9% to 9.1%. Thus, is 0.001. The new price (P, ) is 69.6164 Step 1: y Step 2: Decrease the yield on the bond by 10 basis points from 9% to 8.9%. The new price (P)is 71.1105. Step 3: Because the initial price, Po, is 70.3570, the duration can be approximated as follows: 1.1105 69.6164 approximate duration35 2(70.3570) (0.001) 10.62