(a) The line \(y=3 x-2\) intersects the curve \(2 x^{2}-x y+y^{2}=2\) at the points \(A\) and \(B\). The point \(C\) with coordinates \(\left(k, \frac{7}{8}\right)\) lies on the perpendicular bisector of the line \(A B\). Find the exact value of \(k\). (b) The point \(D\) lies on the perpendicular bisector of \(A B\) such that \(D\) is a reflection of \(C\) in the line \(A B\). Find the coordinates of \(D\).