Today is 1 July 2021. Joan has a portfolio which consists of two differenttypes of financial instruments (henceforth referred to as instrument A and instrumentB). Joan purchased all instruments on 1 July 2015 tocreate this portfolio and this portfolio is composed of 298 units of instrumentA and 475 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 ofj₂= 3.38% p.a. and face value of 100. This bond matures at par. The maturity date is 1 January 2023.

Based on the price in part a and part b, and the duration value in part c,calculate the current duration of Joan's portfolio. Express your answerin terms of years and round your answer to two decimal places.

a.6.44

b.5.83

c.4.40

d.4.34