Suppose NCKU company currently has NTD 10 million of five-year bonds with a coupon rate of 2%, a yield-to-maturity of 3.25%, and a remaining life of two years, and NTD 20 million of ten-year bonds with a coupon rate of 3.5%, a yield-to-maturity of 4.5% and a remaining life of three years. These two bonds pay coupons semi-annually. Assuming the settlement date is January 1, 2022. 

What is the portfolio modified duration of these two bonds using the Aggregate Cash Flow approach? years