Help me with this program please!!

Here is what i need to do, and really need help on the three classes,

An Item class which contains six read-write properties but no methods. The properties are:
IDNumber, String
Description, String
DailyRate, Decimal
WeeklyRate, Decimal
MonthlyRate, Decimal
Quantity, Integer

There should be an Inventory class which contains a single Items property that contains a collection of Item objects. The methods of this class should be:
Public Sub AddItem(ByVal item As Item)
adds a new Item to the inventory
Public Function RemoveItem(ByVal id As String)
removes an Item from the inventory
Public Function GetItem(ByVal id As String) As Item
retrieves and item from the inventory

There should be an InventoryData class which is responsible for reading inventory from a text file into a collection and writing back to the text file from a collection. The text file should be placed in the App_Data folder. The class has no properties but does have private variables that hold a filename, StreamReader, and StreamWriter. The methods should be:
Public Sub New(ByVal filename As String)
constructor which initializes the inventory filename
Public Sub LoadData(ByVal inven As Inventory)
opens and loads the inventory file into the inventory collection
Public Sub SaveData(ByVal invent As Inventory)
opens and saves the inventory collection into the inventory file
Private Function ReadOneItem( ) As Item
reads one item from the inventory file and returns an Item object
this is a "helper" function for LoadData
Private Sub WriteOneItem(ByVal item As Item)
writes an Item object to the inventory file
this is a "helper" function for SaveData

Here is what i did so far in the item class, i am not sure if i have the right code???

Code:

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Imports Microsoft.VisualBasic

Public Class Item
    Private mIDNum As String
    Private mDescription As String
    Private mDailyRate As Decimal
    Private mWeeklyRate As Decimal
    Private mMonthlyRate As Decimal
    Private mQuantity As Integer
    Public Property IDNum() As String
        Get
            Return mIDNum
        End Get
        Set(ByVal inIDNum As String)
            mIDNum = inIDNum
        End Set
    End Property
    Public Property Description() As String
        Get
            Return mDescription
        End Get
        Set(ByVal inDescription As String)
            mDescription = inDescription
        End Set
    End Property
    Public Property DailyRate() As Decimal
        Get
            Return mDailyRate
        End Get
        Set(ByVal inDailyRate As Decimal)
            If inDailyRate > 0 Then
                mDailyRate = inDailyRate
            End If
        End Set
    End Property
    Public Property WeeklyRate() As Decimal
        Get
            Return mWeeklyRate
        End Get
        Set(ByVal inWeeklyRate As Decimal)
            If inWeeklyRate > 0 Then
                mWeeklyRate = inWeeklyRate
            End If
        End Set
    End Property
    Public Property MonthlyRate() As Decimal
        Get
            Return mMonthlyRate
        End Get
        Set(ByVal inMonthlyRate As Decimal)
            If inMonthlyRate > 0 Then
                mMonthlyRate = inMonthlyRate
            End If
        End Set
    End Property
    Public Property Quantity() As Integer
        Get
            Return mQuantity
        End Get
        Set(ByVal inQuantity As Integer)
            If inQuantity > 0 Then
                mQuantity = inQuantity
            End If
        End Set
    End Property

End Class

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