如题：A pension fund manager anticipates that benefits of $1million per year must be paid to retirees. Retirements will not occur until 10 years from now at time t=10. Once benefits begin to be  paid, they will extend until t=39 for a total of 30 payments. What is the present value of the pension liability if the appropriate annual discount rate for plan liabilities is 5 percent compounded annually?
此题为什么用得是期末年金的算法 而不是 起初年金？由10时点以后的年金折现到9时点都比较好理解，就是10-39这段按题意应该是用annuity due算啊……那位好心人能翻译下整题  谢谢了！