An electronic games manufacturer producing
a new product estimates the annual sales to be 8000 units.
Each year, 5% of the units that have been sold will become
inoperative. So, 8000 units will be in use after 1 year,
[8000+ 0.95(8000)] units will be in use after 2 years, and so
on. How many units will be in use after n years?