Jordan content of an $n$-cell

Let $I=[a_1,b_1]\times \mathrm{\cdots }\times [a_n,b_n]$ be an $n$-cell in ${ℝ}^n$. Then the Jordan content (denoted $\mu (I)$) of $I$ is defined as

$$\mu (I):=\prod _{j=1}^n(b_j-a_j).$$