185. Friend Function

A base class has a friend function. A derived class tries to use it:

class Base {
   int secret = 10;
   friend void peek(Base& b);
};

class Derived : public Base {
   int extra = 20;
};

void peek(Base& b) {
   printf("%d", b.secret); // OK -- friend of Base
}

void peek_derived(Derived& d) {
   // printf("%d", d.extra); // Can peek access Derived's private?
}

Can peek access Derived's private member extra?