Класс Аккаунт(наследование)

#ifndef ACCOUNT_H
#define ACCOUNT_H
 
class Account
{
public:
    Account(double);
    void credit(double);
    void debit(double);
    double getBalance() const;
protected:
    double balance;
};
 
#endif

#include <iostream>
using std::cout;
using std::endl;
#include "Account.h"
 
Account::Account(double initBalance)
{
    if(initBalance < 0.0)
    {
        balance = 0.0;
 
        cout << "Invalid initial balance. Initial balance = 0.0" << endl;
    }
    else
        balance = initBalance;
}
 
double Account::getBalance() const
{
    return balance;
}
 
void Account::credit(double amount)
{
    balance += amount;
}
 
void Account::debit(double amount)
{
    if(amount <= balance)
    {
        balance -= amount;
    }
    else
        cout << "Debit amount exceeds account balance" << endl;
}

#ifndef SAVINGSACCOUNT_H
#define SAVINGSACCOUNT_H
 
#include "Account.h"
 
class SavingsAccount : public Account
{
public:
    SavingsAccount(double, double);
    double calculateInterest();
private:
    double interestRate;
};
 
#endif

#include "SavingsAccount.h"
 
SavingsAccount::SavingsAccount(double initBalance, double interest)
    : Account(initBalance), interestRate(interest)
{
    ;
}
 
double SavingsAccount::calculateInterest()
{
    return ;
}

#ifndef CHECKINGACCOUNT_H
#define CHECKINGACCOUNT_H
 
#include "Account.h"
 
class CheckingAccount : public Account
{
public:
    CheckingAccount(double, double);
    void credit();
    bool debit();
private:
    double feeForTheTransaction;
};
 
#endif

#include "CheckingAccount.h"
 
CheckingAccount::CheckingAccount(double initBalance, double fee)
    : Account(initBalance), feeForTheTransaction(fee)
{
    ;
}
 
void CheckingAccount::credit()
{
 
}
 
bool CheckingAccount::debit()
{
 
}