First step: calcualte principal end of year two

Time 0: $1,000,000 -> Time 2: $1,000,000 *( (1+15%/2)^2)^2 = $1,335,469
Time 0.5: $500,000 -> Time 2: $500,000 * ((1+15%/2)^2)^1.5 = $621,148
Time 1: $500,000 -> Time 2: $500,000 * (1+15%/2)^2 = $577,813
Total principal at time 2: $1,335,469 + $621,148 + $577,813 = $2,534,430

Second step: calculate mortgage discount factor

first 5 years (60 months): (1-1.01^-60)/(1-1.01^-1) = 45.4
the rest (300 months): 1.01^-60*(1-1.01^-300)/(1-1.01^-1) = 52.79
However, since from 6 to 30 year, montly payment double => 52.79*2 = 105.58
total discount factor = 45.4+105.58=150.98

Step 3: monthly payment = principal / discount factor = $2,534,430/150.98=$16,787 (c)

Got it! many thanks! 多谢大神

别客气。
说起来这还是我十五年前学习的内容。我还真有点佩服我自己，竟然还能想起来怎么计算。都说考完初级考试后连variance都不会算了，还真有点这种趋势。呵呵。
其实利息理论无非就是计算future value，present value翻过来调过去地折腾。把问题分割成小块再画个时间表就一目了然了。

学霸果然是学霸，这么久的东西还能记得。总之非常感谢你啦～

楼主FM的教材可以发一份给我吗？付论坛币的