Answer
$\$7830.09$
Work Step by Step
We know that $a_n=a_1r^{n-1}.$
where $r$=common ration (we can get this by dividing any two consecutive terms) and $a_1$= the first term
Here $a_1=\$15000$ and $r=0.85$ (because of the $15$ percent price decrease), hence $a_5=a_1(r^{5-1})=\$15000(0.85^4)=\$7830.09$