8. Calculate the answer

If $X$ $=$ $\{x: x$ is a multiple of $2$, $n \in \mathbb{N}$ and $n \le 20\}$, $Y$ $=$ $\{x: x$ is a multiple of $3$, $n \in \mathbb{N}$ and $n \le 20\}$ and $Z$ $=$ $\{x: x$ is a multiple of $6$, $n \in \mathbb{N}$ and $n \le 20\}$, then find $X\cup (Y \cap Z)$.

 

$X \cup (Y \cap Z)$ $=$ $\{$$\}$.

 

[Note: Enter the numbers in ascending order, also insert a comma to separate the numbers]