Let $\mathbb{R}^D$ be a D816: Euclidean real Cartesian product such that

(i)	$\ell^*$ is a D780: Lebesgue outer measure on $\mathbb{R}^D$
(ii)	$E, F \subseteq \mathbb{R}^D$ are each a D5612: Euclidean real set
(iii)	\begin{equation} E \subseteq F \end{equation}

Then \begin{equation} \ell^*(E) \leq \ell^*(F) \end{equation}