Suppose the yield curve is flat at 4%, and you bought 100 4-year, 2% coupon bonds with faces of $1,000, exposing you to IR risk. (a) Calculate your bonds duration (b) If you have access to 10-year strips (F=$1,000), how many should you buy or sell to hedge the interest rate risk? (c) What is the exact change of the value of your portfolio if the yield curve moves up from 4% to 5%?