Виртуальные функции

#include "stdafx.h"
#pragma hdrstop
#include <iostream>
#include <tchar.h>
#include <cmath>
//---------------------------------------------------------------------------
#pragma argsused
using namespace std;
class Figure
{public:
virtual float Volume()=0;
};
class Parallepiped:public Figure
{
float x,y,z;
public:
Parallepiped():x(0),y(0),z(0){};
Parallepiped(float x1,float y1,float z1):x(x1),y(y1),z(z1){};
float Volume(){return x*y*z;}};
 
class Piramida:public Figure
{float x,y,h;
public:
Piramida():x(0),y(0),h(){};
Piramida(float x1,float y1,float h1):x(x1),y(y1),h(h1){};
float Volume(){return x*y*h;}};
 
class Tetraid:public Figure
{float a;
public:
Tetraid():a(0){};
Tetraid(float a1):a(a1){};
float Volume(){return pow(a,3)*pow(2,0.5)/12;}};
 
class Shar:public Figure
{float r;
public:
Shar():r(0){};
Shar(float r1):r(r1){};
float Volume(){return 4*pow(r,3)*3.14/3;}};
 
int _tmain(int argc, _TCHAR* argv[])
 {   Figure* mas[4];
 mas[0]=new Parallepiped(3,4,6);
 mas[1]=new Piramida(5,4,3);
 mas[2]=new Tetraid(27);
 mas[3]=new Shar(3);
 cout<<"1-Параллепипед"<<endl<<"2-Пирамида"<<endl<<"3-Тетраэдр"
 <<endl<<"4-Шар"<<endl<<endl;
 for (int i=0; i < 4; i++) {
  cout<<"Объем фигуры, номер "<<i+1<<" = "<<mas[i]->Volume()<<endl;
 
 }
 
 
  system("pause");
        return 0;
 }

class Piramida :  public Figure
{ double x,y,h;