问题如下：
Remington and Montgomery discuss Isabelle Sebastian. During a recent conversation, Sebastian, a long-term client with a $2,900,000 investment portfolio, reminded Remington that she will soon turn age 65 and wants to update her investment goals as follows:
Goal 1: Over the next 20 years, she needs to maintain her living expenditures, which are currently $120,000 per year (90% probability of success). Inflation is expected to average 2.5% annually over the time horizon, and withdrawals take place at the beginning of the year, starting immediately.
Goal 2: In 10 years, she wants to donate $1,500,000 in nominal terms to a charitable foundation (85% probability of success).
Exhibit 2 provides the details of the two sub-portfolios, including Sebastian’s allocation to the sub-portfolios and the probabilities that they will exceed the expected minimum return.
Exhibit 2 Investment Sub-Portfolios & Minimum Expected Return for Success Rate
Assume 0% correlation between the time horizon portfolios.
Using Exhibit 2, which of the sub-portfolio allocations is most likely to meet both of Sebastian’s goals?
选项：
A. The current sub-portfolio allocation.
B. A 43% allocation to sub-portfolio BY and a 57%
allocation to sub-portfolio CZ.
C. A 37%allocation to sub-portfolio BY and a 63% allocation to sub-portfolio CZ.
解释：
C is correct.
Goal 1 关键词：90% probability of success，20 years。通过查表，选择CZ portfolio，minimum expected return=5.7%。5.7%是名义利率，当前每年生活费$120,000会以2.5%的通货膨胀率增长，所以实际利率=(1+5.7%)/(1+2.5%)-1=3.12%.（近似法：5.7%-2.5%=3.2%也可行，计算结果影响不大。）
计算CZ的PV：由于第一笔现金流发生在0时刻，所以要使用计算器BGN模式：
输入N=20, I/Y=3.12, FV=0,PMT=120,000，得出PV=1,820,738.
Goal 2 关键词：85% probability of success，10 years。通过查表，选择BY portfolio，minimum expected return=3.6%。
计算BY的PV：将期末的$1.5m折到0时刻，得出PV=1,500,000/1.03610=1,053,158。
CZ占比：1,820,738 / 2,900,000=62.78%
BY占比：1,053,158 / 2,900,000=36.32%
所以最接近选项C。
为什么目标1用实际利率折现,目标2用名义利率折现？
