C++设计一个立方体类Box,它能计算并输出立方体的体积和表面积.

#include
using namespace std;
class Box
{
public:
Box(double n){arc=n;}
double V(){return arc*arc*arc;}
double S(){return 6*arc*arc;}
private:
double arc;
};
int main()
{
Box b(3);
cout