The plane \(\Pi\) passes through the points
$$A(-1, -1, 1), B(4, 2, 1) \text{ and } C(2, 1, 0).$$
- Find a vector equation of the line perpendicular to \(\Pi\) which passes through the point \(D(1, 2, 3)\). [3]
- Find the volume of the tetrahedron \(ABCD\). [3]
- Obtain the equation of \(\Pi\) in the form \(\mathbf{r} \cdot \mathbf{n} = p\). [3]
The perpendicular from \(D\) to the plane \(\Pi\) meets \(\Pi\) at the point \(E\).
- Find the coordinates of \(E\). [4]
- Show that \(DE = \frac{11\sqrt{35}}{35}\). [2]
The point \(D'\) is the reflection of \(D\) in \(\Pi\).
- Find the coordinates of \(D'\). [3]