19. In three years an investor deposits the first of eight $1000 payments into a special fund, The fund will earn interest at the rate of 5% per year until the end of the fifth year. Thereafter, all money accumulated in the fund will earn a reduced interest rate of 4% compounded annually until the end of the tenth year. How much money will the investor habe in the fund at the end of ten years assuming no withdrawals are made?

Question 19 - #44978
Your answer: C was correct!
It to best to break this problem into parts to accommodate the change in the interest rate. Money in the
fund at the end of ten years based on deposits made with initial interest of 5%:
(1) The total value in the fund at the end of the fifth year is $3,152.50: PMT = $1,000; N = 3; I/Y = 5; CPT
→ FV = $3,152.50.
(2) The $3,152.50 is now the present value and will then grow at 4% until the end of the tenth
year. We get: PV = -3,152.50; N = 5; I/Y = 4; PMT = 1,000; CPT → FV = $9,251.82

不明白为什么at the end of the fifth year的价值要用n=3  :

PMT = $1,000; N = 3; I/Y = 5; CPT→ FV = $3,152.50.

这里是把第2年末当做事零时刻点

即把第2年的PV=0，则

第3年年末 1个pmt

第4年年末 1个pmt

第5年年末 1个pmt

所以N=3，明白了吗？