public StationaryAirConditioner(
     string manufacturer,
     string model,
     EfficiancyRating requiredEfficiancyRating,
     int powerUsage)
     : base(manufacturer, model)
 {
     this.PowerUsage = powerUsage;
     this.RequiredEfficiancyRating = requiredEfficiancyRating;
     this.ActualEfficiancyRating = this.GetRating(powerUsage);
 }
        public string RegisterStationaryAirConditioner(string manufacturer, string model, EfficiancyRating energyEfficiencyRating, int powerUsage)
        {
            var airConditioner = new StationaryAirConditioner(manufacturer, model, energyEfficiencyRating, powerUsage);

            this.Database.AddAirConditioner(airConditioner);

            string result = string.Format(Messages.RegisterAc, airConditioner.Model, airConditioner.Manufacturer);
            return result;
        }