void FuelNeedsReport::CalcTotalFuel()
{
    Company* company = Company::GetInstance();
    double result = 0;
    
    for (int i=0; i<company->GetIndex(); i++) {
        Vehicle* v = company->GetVehicleByIndex(i);
        result += v->CalcFuelNeeds();
    }
    cout << "[총 필요연료] " << result << endl;
}