Find the derivative of the vector function
$\mathbf r(t) = t\mathbf a \times (\mathbf b + t\mathbf c)$, where
$\mathbf a = \langle -3, 1, -3\rangle$, $\mathbf b = \langle 3, 5, -3\rangle$, and $\mathbf c = \langle 2, -1, 1\rangle$.
$\mathbf r'(t) = \langle$ , , $\rangle$