Let $M = (X, \mathcal{F}, \mu)$ be a D1158: Measure space such that

(i)	$E_1, \ldots, E_N \in \mathcal{F}$ are each a D1109: Measurable set in $M$

Then $\mu(\bigcup_{n = 1}^N E_n) < \infty$ if and only if \begin{equation} \mu(E_1), \ldots, \mu(E_N) < \infty \end{equation}