9 With respect to a fixed origin \(O\), the points \(A ( - 1,5,1 ) , B ( 1,0,3 ) , C ( 2 , - 1,2 )\) and \(D ( 3,6 , - 1 )\) are the vertices of a tetrahedron.
- Find the volume of the tetrahedron \(A B C D\).
The plane \(\Pi\) contains the points \(A , B\) and \(C\).
- Find a cartesian equation of \(\Pi\).
The point \(T\) lies on the plane \(\Pi\).
The line \(D T\) is perpendicular to \(\Pi\).
- Find the exact coordinates of the point \(T\).