4. The transformation \(T\) in the plane consists of a translation in which the point \(( x , y )\) is transformed to the point ( \(x + 2 , y - 2\) ), followed by a reflection in the line \(y = x\).
- Determine the \(3 \times 3\) matrix which represents \(T\).
- Determine how many invariant points exist under the transformation \(T\).