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The major idea of the solution is that the FUTURE VALUE of so organized saving plan is the sum of FUTURE VALUES of 3 (three) annuities.
First annuity is 30 years ordinary annuity with the annual deposits of $4500 at 4% APY.
The second annuity is 20 years ordinary annuity with the annual deposits of $4500 at 4% APY.
And the third annuity is 10 years ordinary annuity with the annual deposits of $4500 at 4% APY.
The first annuity starts "this" year (or, better to say, it starts "today" with the first deposit at the end of "this"year);
the second annuity starts 10 years after; and the third annuity starts 20 years after.
You can EASILY understand why it is so, by splitting each $9000 deposits in two deposits by $4500 each:
- then you continue the first annuity with $4500 deposits every year from 11-th year till 20-th year,
- and you starts the second annuity with $4500 deposits annually from the year 11-th till 20-th.
And then splitting each $13500 deposits in three deposits by $4500 each:
- then you continue the first annuity with $4500 deposits every year from 21-th year till 30-th year inclusively,
- then you continue the second annuity with $4500 deposits every year from 21-th year till 30-th year inclusively,
- and you starts the third annuity with $4500 deposits annually from the year 21-th till 30-th inclusively.
Thus the total future value after 30 years will be
FV = FV1 + FV2 + FV3, where
FV1 = future value of the 4% annuity with $4500 deposits during 30 years;
FV2 = future value of the 4% annuity with $4500 deposits during 20 years;
FV3 = future value of the 4% annuity with $4500 deposits during 10 years.
The rest is just a technique.
FV1 = = = 252382.22;
FV2 = = 134001.36
FV3 = = 54027.75.
Now the answer is the sum 252382.22 + 134001.36 + 54027.75 = 440411.33 dollars.
ANSWER. 440411.33 dollars.
Solved.