public override string ToString() { StringBuilder simCardsDescription = new StringBuilder(); _simCards.ForEach(simCard => simCardsDescription.Append(simCard.GetDescription() + "\n")); return($"Mobile phone model: {MobileModel}.\n" + Screen.GetDescription() + "\n" + Microphone.GetDescription() + "\n" + Battery.GetDescription() + "\n" + Speaker.GetDescription() + "\n" + simCardsDescription + "\n" + "\n"); }