public GSM(string model, string manufacturer)
{
this.Model = model;
this.Manufacturer = manufacturer;
this.Price = null;
this.Owner = null;
this.battery = null;
this.display = null;
this.callHistory = new List<Call>();
}
public GSM(string model, string manufacturer, decimal? price, string owner , Battery battery, Display display)
{
this.Model = model;
this.Manufacturer = manufacturer;
this.Price = price;
this.Owner = owner;
this.Battery = battery;
this.Display = display;
}
