Today is 1 July 2020. Joan has a portfolio which consists of two different types of financial instruments (henceforth referred to as instrument A and instrument B). Joan purchased all instruments on 1 July 2011 to create this portfolio and this portfolio is composed of 28 units of instrument A and 44 units of instrument B. Instrument A is a zero-coupon bond with a face value of 100. This bond matures at par. The maturity date is 1 January 2030. Instrument B is a Treasury bond with a coupon rate of j2 = 2.16% p.a. and face value of 100. This bond matures at par. The maturity date is 1 January 2023. . (C) What is the duration of instrument B? Express your answer in terms of years and round your answer to three decimal places. Assume the yield rate is j2 = 4.03% p.a. Select one: a. 5.837 O b. 4.891 c. 2.918 O d. 2.446