How To Use Select Case In Console Application?

Use Of Select Case In Console Application...

Sub Main()
        Dim s1, s2, s3, tot As Integer
        Dim per As Double
       Console.WriteLine("Enter the mark of First Subject out of 100")
        s1 = Console.ReadLine()
       Console.WriteLine("Enter the mark of Second Subject out of 100")
        s2 = Console.ReadLine()
       Console.WriteLine("Enter the mark of Third Subject out of 100")
        s3 = Console.ReadLine()
        tot = s1 + s2 + s3
        per = (tot / 300) * 100
       Console.WriteLine("Your Total is:=>" & tot)
       Console.WriteLine("your Percentage is:=>" & per)

        Select Case (per)
            Case Is < 40
               Console.WriteLine("Grade:=>Fail")
               Console.ReadLine()
            Case 40 To 50
               Console.WriteLine("Grade:=>Second Class")
               Console.ReadLine()
            Case 50 To 60
               Console.WriteLine("Grade:=>First Class")
               Console.ReadLine()
            Case Is > 70
               Console.WriteLine("Grade:=>Distionction")
               Console.ReadLine()
        End Select
End Sub