Part A.
Since she will earn an additional $8,000 per year, then after 40 years she will have
[tex]\text{ \$8,000}\times40=\text{ \$ 320,000}[/tex]
So, the total amount of the additional earning is $320,000
Part B.
In this case, we need to use the compound interest formula, given by
[tex]A=P(1+\frac{r}{n})^{n\cdot t}[/tex]
where A is the future value, P is the present value, r is the annual interest rate, n is the number of compounding periods per year and t is the time. In our case,
[tex]\begin{gathered} P=\text{ \$320,000} \\ r=0.06 \\ n=1 \end{gathered}[/tex]
Then, by substituting these values into the formula, we have
