Public Class Person
    Private Name1 As String
    Private Name2 As String

    Public Property FirstName() As String
        Get
            Return Name1
        End Get
        Set(ByVal Value As String)
            Name1 = Value
        End Set
    End Property

    Public Property LastName() As String
        Get
            Return Name2
        End Get
        Set(ByVal Value As String)
            Name2 = Value
        End Set
    End Property

    Public Function Age(ByVal Birthday As Date) As Integer
        Return Int(Now.Subtract(Birthday).Days / 365.25)
    End Function
End Class

Public Class Teacher
    Inherits Person
    Private Level As Short

    Public Property Grade() As Short
        Get
            Return Level
        End Get
        Set(ByVal Value As Short)
            Level = Value
        End Set
    End Property
End Class
