Suppose an Electronic Games Manufacturer Producing a New Product Estimates $20 \%$

Suppose an electronic games manufacturer producing a new product estimates the annual sales to be 4,000 units. Each year $20 \%$ of the units that have been sold will become inoperative. So, 4,000 units will be in use after 1 year, $[ 4,000 + 0.80 ( 4,000 ) ]$ units will be in use after 2 years, and so on. How many units will be in use after $n$ years?

A) $20,000 \left( 1 - 20 ^ { n } \right)$ units
B) $40,000 \left( 1 - 0.80 ^ { n } \right)$ units
C) $\left( 1 - 0.80 ^ { n } \right)$ units
D) $20,000 \left( 1 + 0.80 ^ { n } \right)$ units
E) $\left( 1 + 0.80 ^ { n } \right)$ units