Hello, I am trying to find the domain of the vector function:

I know that for $\displaystyle \ln(7t)$ we have $\displaystyle t\ge 0$, $\displaystyle \sqrt{t+12} \Rightarrow t\ge-12,\frac{1}{\sqrt{19-t}} \Rightarrow t\le18$

So I thought the domain was from [-12,0,]U[0,18] but it isn't correct.

What am I doing wrong?

Thanks,

Matthew