A company must make a payment of $18,983 in 11 years. The market interest rate is 6%. The companys portfolio manager wishes to fund the obligation using four-year zero-coupon bonds and perpetuities paying annual coupons.

How can the manager immunize the obligation?

Suppose that three years have passed, and the interest rate remains at 6%. Is the position still fully funded? Is it still immunized? If not, what actions are required?