What does this C++ snippet output?

1#include <iostream>
2 
3struct Base { virtual int rank() { return 5; } };
4struct Derived : Base {
5  int rank() override { return Base::rank() * 2; }
6};
7int main() {
8    Derived d;
9    Base& b = d;
10    std::cout << b.rank() << "\n";
11}