how we find the estimate convexity?

A risk manager is evaluating the price sensitivity of an investment-grade callable bond. The manager gathers the following information on the bond as well as on the embedded option: Assuming the current interest rate curve is flat at 4%, what is the estimated effective convexity of the callable bond? 18.0 36.0 179.0 719.2 D D is correct. Effective convexity measures the sensitivity of the duration measure to changes in interest rates. It is given by the formula: C=P1[(r)2P++P2P] where P is the value of the bond when all rates increase by r and Pis the value of the bond when all rates decrease by r. Therefore, the best estimate of convexity is: C=97.89101[0.0005297.8566+97.9430297.8910]=719.1672