Objects and Classes - General Questions

A friend function of a class:

What will be the output of the program?

#include <iostream>
using namespace std;
class C {
public:
    static int n;
    C() { n += 2; }
};
int C::n = 1;
int main() {
    C a, b;
    cout << C::n << endl;
    return 0;
}

What will be the output of the program?

#include <iostream>
using namespace std;
class P {
    int v;
public:
    P(int x) : v(x) {}
    friend int peek(const P &p);
};
int peek(const P &p) { return p.v; }
int main() { cout << peek(P(42)) << endl; return 0; }

What will be the output of the program?

#include <iostream>
using namespace std;
class A {
public:
    int x = 1;
    A& add(int n) { x += n; return *this; }
};
int main() {
    A a;
    a.add(2).add(3);
    cout << a.x << endl;
    return 0;
}

What will be the output of the program?

#include <iostream>
using namespace std;
class P {
    mutable int reads = 0;
    int v = 5;
public:
    int get() const { ++reads; return v; }
    int count() const { return reads; }
};
int main() {
    P p;
    p.get(); p.get();
    cout << p.count() << endl;
    return 0;
}