Answer
The answer is $\$793583$.
Work Step by Step
The first year salary $=\$24,000$.
Salary increases by $5\%$ each year.
Next salary $105%$ of first salary
$=24,000\cdot 1.05 =\$25,200 $
This is the geometric sequence.
Common ratio $r=1.05$.
Total lifetime salary over the $20-$ year period is
$=\frac{24,000(1-1.05^{20})}{1-1.05}$
Simplify.
$=793582.898469$
Round to the nearest dollar.
$=\$793583$.