public string ManufactureTank(string name, double attackPoints, double defensePoints) { Tank tank = new Tank(name, attackPoints, defensePoints); if (this.machines.Contains(tank)) { return(string.Format(OutputMessages.MachineExists, name)); } tank.CalculatePoints(); this.machines.Add(tank); string result = string.Format(OutputMessages.TankManufactured, name, tank.AttackPoints, tank.DefensePoints, tank.DefenseMode == true ? "ON" : "OFF"); return(result); }