Can someone please help me with this question? My teacher told me my answer was wrong but didn't tell me why, how or what the right answer was. Please help.

29. You find a bond with 19 years until maturity that has a coupon rate of 8 percent and a yield to maturity of 7 percent. What is the Macaulay duration? The modified duration?

30. Suppose the yield to maturity on the bond in Problem 29 increases by .25 percent . What is the new price of the bond using duration? What is the new price of the bond using the bond pricing formula? What if the yield to maturity increases by 1 percent? By 2 percent? By 5 percent? What does this tell you about using duration to estimate bond price changes for large interest rate changes?