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4. Consider a bond of face value $1,000 with an annual coupon of 8.0% and 10 years to maturity and a present price of $877.11. Assume the yield curve is flat at 10%. a. Calculate the duration and convexity for this bond. b. Suppose your portfolio consists of this bond only and you want to immunize your interest risks. And suppose you can only buy or sell 1 zero-coupon bond. What should be the maturity of this zero-coupon bond? (Hint: consider now only - in the future, you can rebalance.)