public Address _originAddress; // Origin address

        #endregion Fields

        #region Constructors

        // Preconditions: None
        // Postconditions: The parcel item is initialized with the specified values for origin address and destiation address
        public Parcel(Address theOriginAddress, Address theDestinationAddress)
        {
            OriginAddress = theOriginAddress;
            DestinationAddress = theDestinationAddress;

            CalcCost();
        }
 // Preconditions: None
 // Postconditions: The letter item has been initialized with the spcified values for origin address, destination
 //                 address, and fixed costs
 public Letter(Address theOriginAddress, Address theDestinationAddress, decimal theFixedCosts)
     : base(theOriginAddress, theDestinationAddress)
 {
     fixedCosts = theFixedCosts;
 }