Tom deposited $5,000 into an account monthly, with the first deposit at the end of January 1987 and the last deposit at the end of December 2006 (there were a total of 240 $5,000 deposits). He also made a
one-time deposit into the same account at the end of December 2000 (this was in addition to the $5,000
monthly deposit). Then he withdrew $20,000 from the account monthly, with the first withdrawal at the
end of January 2007. Just after his last withdrawal at the end of December 2021 (there were a total of
180 $20,000 withdrawals), there was $180,000 remaining in the account. The account used to earn
interest at an annual rate of 6 percent compounded monthly. What should be the amount of the one-time
deposit at the end of December 2000?