What will be the output of the following C++ code?

#include <iostream>
using namespace std;
class sample 
{
    int width, height;
    public:
    void set_values (int, int);
    int area () {return (width * height);}
    friend sample duplicate (sample);
};
void sample::set_values (int a, int b) 
{
    width = a;
    height = b;
}
sample duplicate (sample rectparam)
{
    sample rectres;
    rectres.width = rectparam.width * 2;
    rectres.height = rectparam.height * 2;
    return (rectres);
}  
int main ()  
{
    sample rect, rectb;
    rect.set_values (2, 3);
    rectb = duplicate (rect);
    cout << rectb.area();
    return 0;
}

A. 20

B. 16

C. 24

D. 18

Answer: Option C