Today is 1 July 2019. Jenny has a portfolio which consists of three different types of financial instruments (henceforth referred to as instrument A, instrument B and instrument C. Jenny purchased all instruments on 1 July 2017 to create this portfolio and this portfolio is composed of 50 units of instrument A, 78 units of instrument B and 105 units of instrument C)

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.

What is the duration of instrument A? Express your answer in terms of years and round your answer to three decimal places. Assume the yield rate is j2 = 3.3% p.a.