Matrices And Determinants

If $a$ and $b$ are any two real numbers, then

$$ \left|\begin{array}{ccc} 2 a-2 b-4 & 4 a & 4 a \\ 4 & 2-b-a & 4 \\ 2 b & 2 b & b-a-2 \end{array}\right|= $$