Counts the time needed to say all numbers up to 1 billion

OneBillion.vb

Imports System.Threading

Module OneBillion

  'Time needed to say numbers (in milliseconds)
    Const unit = 158 'From 0-9
    Const tens = 262 ' From 10-90
    Const magnitude = 282 'time to say 'hundred, thousand, million'

    Sub Main()
        Dim summative As Long = 0

        'Optimising this loop is left as an exercise to the reader 
        '(Hint: If it takes n seconds to say 'one hundred' and m seconds to say all numbers from 0-99, 
        'it takes 100n + m seconds to say all numbers from 100-199)
        Parallel.For(0, 1000000000,
                     Sub(index As Integer)
                         Dim sumTime = CountTimeToSay(index.ToString("D10"))
                         Interlocked.Add(summative, sumTime)
                     End Sub)
        Console.WriteLine(summative / 1000 & " seconds")
        Console.Read()

    End Sub

    'I don't want to see this on r/badcode
    Function CountTimeToSay(number As String) As Integer

        Dim sumTime As Integer = 0
        Dim Arr = number.ToArray

        If Arr(9) <> "0" Then        'Units
            sumTime += unit
        End If
    
        If Arr(8) <> "0" AndAlso Arr(8) <> "1" Then   'Tens, but treating the teens as units only
            sumTime += tens
        End If
    
        If Arr(7) <> "0" Then        'Hundreds
            sumTime += magnitude + unit
        End If
    
        If Arr(6) <> "0" Then        'Thousands
            sumTime += magnitude + unit
        ElseIf New String(Arr.Skip(4).Take(2).ToArray) <> "00" Then 'Checks to make sure a thousands value actually exists before adding the magnitude for it
            sumTime += magnitude
        End If
    
        If Arr(5) <> "0" Then        'Ten Thousands
            sumTime += tens
        End If
    
        If Arr(4) <> "0" Then        'Hundred Thousands
            sumTime += magnitude + unit
        End If
    
        If Arr(3) <> "0" Then        'Millions
            sumTime += magnitude + unit
        ElseIf New String(Arr.Skip(1).Take(2).ToArray) <> "00" Then
            sumTime += magnitude
        End If
    
        If Arr(2) <> "0" Then        'Ten Millions
            sumTime += tens
        End If
    
        If Arr(1) <> "0" Then        'Hundred Millions
            sumTime += magnitude + unit
        End If
        If Arr(0) <> "0" Then        'Billions
            sumTime += magnitude + unit
        End If

        Return sumTime

    End Function
End Module