How to find volume of cylinder using friend function?

CODE

How to find volume of cylinder using friend function?

//Write a program to find volume of cylinder using friend function…

#include<iostream>

using namespace std;

class data

{

    float r,h;

public:

    void input()

    {

        cout<<"\n enter r and h:";

        cin>>r>>h;

    }

    friend void volume(data obj);

};

void volume(data obj)

{

    float v=obj.r*obj.h*3.14*obj.r;

    cout<<"\n volume="<<v;

}

int main()

{

    data obj;

    obj.input();

    volume(obj);

}

Output:

enter r and h:2

6

 volume=75.36