A pension fund has an average duration of its liabilities equal to 17 years. The fund is looking at 5-year maturity zero-coupon bonds and 4% yield perpetuities to immunize its interest rate risk. How much of its portfolio should it allocate to the zero-coupon bonds to immunize if there are no other assets funding the plan? Options: 42.86% 57.14% 29.41% 26.00%