Can a public virtual function in base class be private in derived class?

Question | Aug 7, 2019 | nwheeler 

An overridden virtual function in a derived class can be called in polymorphic manner through the base class reference or pointer. But, can the derived class have a more restrictive access specifier on an overridden virtual function than the base class?

In our example code the class Rectangle overrides its base class Shape's virtual function area:

class Shape {
public:
 virtual int area() {
    return 0;
 };
};

class Rectangle : public Shape {
public:
 Rectangle(int w, int l)
    :width(w),length(l){}
private:
 int area() override {  // <--- It's private
    return width*length;
 }

 int width{0}, length{0};
};

Note that Rectangle::area is declared private, whereas Shape::area is public. The Rectangle is instantiated somewhere and the function area is called on the base class, Shape, pointer as follows:

Shape* ptrShape = new Rectangle(10,20);
std::cout << ptrShape->area() << "\n";

What is the outcome of above code? Select below:

2015 nextptr