How to show: $l^*(A)\le l^*(G_\epsilon)\le l^*(A)+\epsilon $ , $l^* $:outer measure

Question

If $A$ s a Lebesgue measurable subset of $\mathbb{R}$ and $\epsilon\gt 0$

How to show: $\exists$ an open set $G_\epsilon \supset A$ such that

$l^*(A)\le l^*(G_\epsilon)\le l^*(A)+\epsilon $, $l^* $:outer measure