public static void CallHistoryTestPrint() { var myPhone = new Gsm( "THL", "China", "Niki", 200.5M, new Battery(BatteryType.Li_Ion, 60, 20), new Display(5.5M, 16000000)); Console.WriteLine(myPhone); myPhone.AddCall(DateTime.Now, 0885998877, 65); myPhone.AddCall(DateTime.UtcNow, 0885665544, 98); myPhone.AddCall(DateTime.Now, 0885552277, 158); myPhone.AddCall(DateTime.Now, 0885996857, 112); myPhone.AddCall(DateTime.Now, 0885995827, 87); Console.WriteLine(myPhone.CallHistory); var priceInfo = new StringBuilder(); priceInfo.AppendFormat("Total price: {0:C2}", myPhone.CallPrice()); myPhone.RemoveLongestCall(); priceInfo.AppendFormat(Environment.NewLine); priceInfo.AppendFormat("Longest Call removed"); priceInfo.AppendFormat(Environment.NewLine); priceInfo.AppendFormat("Total price: {0:C2}", myPhone.CallPrice()); myPhone.ClearCallHistory(); Console.WriteLine(priceInfo); Console.WriteLine(myPhone.CallHistory); }