A pension plan will have a cash outflow in 3 years. They can invest in 2 year bonds with a duration of 1.7 years and 4 year bonds with a duration of 3.5 years. To immunize the portfolio, the proportion invested in the 4 year bonds should be

A) 0.44

B) 0.28

C) 0.50

D) 0.72

Please show all work and steps