Answer:
Explanation:
we know that
The simple interest formula is equal to
where
A is the Final Investment Value
P is the Principal amount of money to be invested
r is the rate of interest
t is Number of Time Periods
in this problem we have
substitute in the formula above
Remember that Interest is equal to
![I=A-P](https://img.qammunity.org/2020/formulas/mathematics/middle-school/rvdb3mvr1zn14f0ml8xsruu706m8aiqgv3.png)
![I=\$421.60-\$400=\$21.60](https://img.qammunity.org/2020/formulas/mathematics/high-school/exmiu4tte22hstsirhp4er4mbl5lde7028.png)