C++// Rectangle.cpp is the Rectangle class function implementation file.#include \"Rectangle.h\"/******************************************************************* *          Rectangle::setLength             * * If the argument passed to the setLength function is zero or   * * greater, it is copied into the member variable length, and true * * is returned. If the argument is negative, the value of length  * * remains unchanged and false is returned.            * *******************************************************************/bool Rectangle::setLength(double len){    bool validData = true;  if (len >= 0)        // If the len is valid   length = len;      // copy it to length  else   validData = false;    // else leave length unchanged   return validData;}/****************************************************************** *          Rectangle::setWidth             * * If the argument passed to the setWidth function is zero or   * * greater, it is copied into the member variable width, and true * * is returned. If the argument is negative, the value of width  * * remains unchanged and false is returned.            * ******************************************************************/bool Rectangle::setWidth(double w){    bool validData = true;  if (w >= 0)         // If w is valid   width = w;        // copy it to width  else   validData = false;    // else leave width unchanged   return validData;}/************************************************************** *           Rectangle::getLength          * * This function returns the value in member variable length. * **************************************************************/double Rectangle::getLength(){    return length;}/************************************************************** *           Rectangle::getWidth          * * This function returns the value in member variable width. * **************************************************************/double Rectangle::getWidth(){    return width;}/******************************************************************* *            Rectangle::getArea            * * This function calculates and returns the area of the rectangle. * *******************************************************************/double Rectangle::getArea(){    return length * width;}