Final answer:
Without additional data on transactions or returns, we assume the investment account balance would remain at the beginning balance of $630,000 by December 31, 2021.
Step-by-step explanation:
The question concerns calculating the ending balance of an investment account given a starting balance but without additional information about possible transactions or interest rates. To determine the balance of an investment account at a specific date, such as December 31, 2021, we must consider any additional contributions, withdrawals, and the return on the investment - whether that is interest, dividends, or capital gains.
Without such information, it's not possible to accurately calculate the ending balance of the investment. Financial transactions throughout the year, the interest rate, or the return generated by the investments can significantly alter the balance.
If no additional information is provided, and assuming there are no transactions or earnings in the account, the balance at December 31, 2021, would remain the same as the beginning balance of $630,000. However, this is a simplified assumption, as investment accounts typically have some form of activity or returns.