A portfolio manager wants to use 2-year zero coupon bonds and perpetuities with a yield to maturity of 7.5% per year to immunize a liability with a duration of 7 years. What percent of the portfolio should she invest in the zero-coupon bonds? 1) 59.4% 2) 40.6% 3) 44.6% 4) 54.8% 5) 62.2%