Answer
No.
Work Step by Step
The given values are
Initial value $=\$20,000$.
Growth factor $=1-0.20=0.80$.
Time period $x=6\;yr$.
The value after $6\;yr$ is
$=20,000 \cdot (0.80)^6$
Simplify.
$=5242.88$
Hence, they can't sell it for $\$4000$.