A friend function is a non-member function that is allowed to access a class's private members. Create a class Wallet with a private double balance set by its constructor.

Requirements:
1) Constructor Wallet(double b) that stores b in balance.
2) Declare a friend function inside the class: friend double getBalance(const Wallet& w);
3) Define getBalance as a normal free function (NOT a member) that returns w.balance.

Do NOT write a main function.