Today is 1 July, 2019. Siobhn has a portfolio which consists of two different types of financial instruments (henceforth referred to as instrument A and instrument B). Siobhn purchased all instruments on 1 July 2014 to create this portfolio, which is composed of 20 units of instrument A and 24 units of instrument B.

• Instrument A is a zero-coupon bond with a face value of $100. This bond matures at par. Its maturity date is 1 January 2029.
• Instrument B is a Treasury bond with a coupon rate of j₂=4.16% p.a. and a face value of $100. This bond matures at par. Its maturity date is 1 January 2022.

Calculate the current duration of Siobhns portfolio using a yield to maturity of j₂=3.89% p.a. Express your answer in terms of years and round your answer to two decimal places.

a.

4.89 years

b.

4.99 years

c.

6.27 years

d.

6.77 years