#### Answer

$\color{blue}{36a^2b^4c^7\sqrt{ac}}$

#### Work Step by Step

Factor the radicand so that at least one factor is a perfect square:
$=\sqrt{(1296a^4b^8c^{14})(ac)}
\\=\sqrt{(36a^2b^4c^7)^2(ac)}$
Bring out the square root of the perfect square factor to obtain:
$=\color{blue}{36a^2b^4c^7\sqrt{ac}}$