$$n ( A ) = 10 , n ( B ) = 6 n ( A U B ) = 12 , n ( A n B ) = \cdots \cdots \cdots \cdots$$
$n=60U\text{, }A=\frac{1}{6U}\text{, }B\in \mathrm{R}\text{, }U\neq 0$
$n\neq 0\text{, }A=\frac{10}{n}\text{, }B=0\text{, }U\in \mathrm{R}$
