How to find volume of cylinder using friend class with 2 classes?

CODE

How to find volume of cylinder using friend class with 2 classes?

//Write a program to find volume of cylinder using friend class with 2 classes..

#include<iostream>

using namespace std;

class data2;

class data1

{

    float r;

public:

    void input()

    {

        cout<<"\n enter r:";

        cin>>r;

    }

    friend class pro;

};

class data2

{

    float h;

public:

    void input()

    {

        cout<<"\n enter h:";

        cin>>h;

    }

    friend class pro;

};

class pro

{

public:

    void volume(data1 obj1,data2 obj2)

    {

        float v=3.14*obj1.r*obj1.r*obj2.h;

        cout<<"\n volume="<<v;

    }

};

int main()

{

    data1 obj1;

    data2 obj2;

    obj1.input();

    obj2.input();

    pro p;

    p.volume(obj1,obj2);

}

Output:

enter r:4

 enter h:8

 volume=401.92