Identify the valid and invalid overloaded methods in the following code:

public class PointD { private double x; private double y; // method 1 public double distance (PointD pt) { // method 2 public static double distance (PointD pt) { } // method 3 public static double distance (PointD pt1, PointD pt2) { // method 4 public double distance (PointD pt1, PointD pt2) { }, // method 5 public PointD middle (PointD pt) { } * // method 6 public PointD middle (PointD pt1, PointD pt2) { } // method 7 public PointD middle (PointD pt1, PointD pt2, PointD pt3) { } // method 8 public PointD product (PointD pt) { }, // method 9 public double product (PointD pt) { } * // method 10 public PointD product (double scalar) { } // method 11 public PointD product (PointD pt, double scalar) { ... } // method 12 public PointD product (double scalar, PointD pt) { }