Answer:
After n years, 120,000(1 - 0.92ⁿ) units, will be in use.
Step-by-step explanation:
Given;
estimated annual sales, a = 9600 units
determine common ratio, r;
[tex]r = 1 - \frac{8}{100}\\\\r = 0.92[/tex]
sum of the units in use after n years is calculated by applying sum of nth term;
[tex]S_n = \frac{a}{1-r} (1-r^n)[/tex]
[tex]S_n = \frac{9600}{1-0.92} (1-0.92^n)\\\\S_n = \frac{9600}{0.08} (1-0.92^n)\\\\S_n = 120,000(1-0.92^n) \ units[/tex]
Therefore, after n years, 120,000(1 - 0.92ⁿ) units, will be in use.