6 Points \(A , B\) and \(C\) have coordinates \(A ( - 3,7 ) , B ( 5,1 )\) and \(C ( - 1 , k )\), where \(k\) is a constant.
- Given that \(A B = B C\), calculate the possible values of \(k\).
The perpendicular bisector of \(A B\) intersects the \(x\)-axis at \(D\).
- Calculate the coordinates of \(D\).