namespace Packt.CloudySkiesAir.Chapter9 {
public class MileageTracker {
    private const int SignUpBonus = 100;
    public int Balance { get; set; } = SignUpBonus;

    public void AddMiles(int miles) {
      Balance += miles;
    }

    public bool RedeemMiles(int miles) {
      if (Balance >= miles) {
        Balance -= miles;
        return true;
      }
      return false;
    }
  }
}