Equlibrium measure of a product subset of ${\mathbb{C} }^{n}$

In this note we show that an equilibrium measure of a product of two subsets of ${\mathbb{C} }^{n}$ and ${\mathbb{C} }^{m}$, respectively, is a product of their equilibrium measures. We also obtain a formula for $(dd^{c}\max \{u,v\})^{p}$, where $u,v$ are locally bounded plurisubharmonic functions and $2\leq p\leq n$.