Exercise 3. The following exercises refer to the rectangle class Rect declaration in the header file shown below. class Rect public: Rect(int len, int wid); int GetArea(); // return the area of the rectangle 1/ space for adding new member functions private: int length; int width; (a) Define the constructor Rect(int len, int wid); in the implementation file. (b) Write the implementation for member function int GetArea () (e) Declare and implement a new method (function member) bool isItASquare () to check if the Rect object is a square. (d) Declare and implement a new method (function member) void display (ostream& out) const so that it can be used to print a Rect object in the format [length, width). For example: Rect r(5, 3); r.display (cout); // it should print the Rect r as [5, 3] on the screen