Final answer:
The interest amount earned by Lee Sun is $-7886.86.
Step-by-step explanation:
To calculate the interest amount, we need to find the difference between the present balance and the previous balance.
The deposits and withdrawals are not relevant in this case.
The formula for compound interest is:
Interest = Present Balance - Previous Balance
Therefore, the interest amount Lee Sun earned is $13,508.79 - $21,395.65 = $-7886.86.