Rich Uncle Bob left you an inheritance of $500,000. You invest these funds in an investment account earning 4% annual compound interest. At the beginning of each year (including Year 1), you withdraw $40,000 to live on. At the beginning of Year 3, only once, you withdraw $80,000. Which year (example "year 8) will you not be able to take your normal $40,000 withdraw because you've run out of money?

How can you solve this on a financial calulcator? If possible?