The coordinates of the points \(A\), \(B\) and \(C\) relative to a fixed origin \(O\) are \((1, 2, 3)\), \((-1, 3, 4)\) and \((2, 1, 6)\) respectively. The plane \(\Pi\) contains the points \(A\), \(B\) and \(C\).
- Find a cartesian equation of the plane \(\Pi\).
[5]
The point \(D\) has coordinates \((k, 4, 14)\) where \(k\) is a positive constant.
Given that the volume of the tetrahedron \(ABCD\) is 6 cubic units,
- find the value of \(k\).
[4]