Today is 15 May 2020, Sue just purchased a Treasury bond with a coupon rate of 12 = 3.2% p.a. and a face value of $100 that matures at par. The maturity date of this bond is 15 May 2022. Assume that we do not know her purchase price. c) Calculate the duration of this Treasury bond. Assume the yield rate is 12 = 3.68% p.a. Give your answer in terms of years, rounded to four decimal places. Select one: a. 3.9021 b. 3.9060 c. 1.9530 d. 1.9511