1. TOM: annualy saves 'A' with 4% of compound interest (18years = doubled)

2. He'll save for 36 years, and after that, he will retire.

3. After that, the entire amount will not withdraw from the above product, but TOM will be use only 3A every year.

4. How balance does he have after 36 years?

TIMELINE-----------------------------------

0~36Y (saving 'A' per year) /retire/ 36Y~72Y (Spent '3A' per year)

WHEN 72th Year come, How balance does he have?

----------------------------------------------