#include <iostream>
 
using namespace std;
 
class shape
{
public:
    void setHigh(double _high)
    {
        high = _high;
    }

    void setWidth(double _width)
    {
        width = _width;
    }

public:
    double high;
    double width;
};

class cost
{
public:
    int getCost(double area)
    {

        
 
return area * 2;
    }

};

class rectangle : public shape
{
public:
    double getarea()
    {
        return high * width;
    }
};

class rectangleCost : public shape, public cost
{
public:
    double getarea()
    {
        return high * width;
    }
};

int main ()
{
    rectangle rect;
    rect.setHigh(
 
2);
    rect.setWidth(4);

    double area = rect.getarea();
    cout << "面積：" << area << endl;

    rectangleCost rectCost;
    rectCost.setHigh(2);
    rectCost.setWidth(5);

    double area_c = rectCost.getarea();
    double cost = rectCost.getCost(area_c);
     cout << "面積 ：
 
" << area_c << endl;
    cout << "花費 ：" << cost << endl;


   return 0;
}

輸出結果：

面積：8
面積 ：10
花費 ：20