"Simple interest" means the interest goes into a separate bucket, and
it just waits there for you to come and get it. It doesn't get added to the
amount in the account, so next year, you don't get interest on the interest.
4 percent of $2000 is (0.04 x 2000) = $80 .
That's how much interest you get each year.
At the end of 4 years, you have (4 x $80) = $320 in the interest bucket.
(And of course, you still have the original $2000 in the account.)
