Соответствие ООП

class SavingsAccount
{
public:
    SavingsAccount(const double);
    static void modifyInterestRate(const double);
    double calculateMonthlyInterest();
    void setBalance();
    void print();
 
private:
    double savingBalance;
    static double annualInterestRate;
}

#include <iostream>
using namespace std;
#include "SavingsAccount.h"
 
double SavingsAccount::annualInterestRate = 0;
 
SavingsAccount::SavingsAccount(const double b)
{
    savingBalance = b;
}
 
void SavingsAccount::modifyInterestRate(const double proc)
{
    annualInterestRate = proc;
}
 
double SavingsAccount::calculateMonthlyInterest()
{
    return savingBalance * annualInterestRate / 12;;
}
 
void SavingsAccount::setBalance()
{
    savingBalance += calculateMonthlyInterest();
}
 
void SavingsAccount::print()
{
    cout << "Сумма на счету: " << savingBalance << endl
        << "Процент за месяц: " << calculateMonthlyInterest() << endl;
    setBalance();
    cout << "Текущая сумма: " << savingBalance << endl << endl;
}

#include <iostream>
using namespace std;
#include "SavingsAccount.h"
 
int main()
{
    setlocale(LC_ALL, "Rus");
 
    double a;
    SavingsAccount saver1(2000);
    SavingsAccount saver2(3000);
 
    cout << "Введите процент: " << endl;
    cin >> a;
    cout << endl;
    saver1.modifyInterestRate(a);
 
    saver1.print();
    saver2.print();
 
    system("pause");
    return 0;
}

SavingsAccount::modifyInterestRate(a);