Вычисление значения выражения - Visual Basic .NET

Imports System.Console
Module Module1
    Dim sum, a, k, b, x, y As Double
    Dim j As Integer
    Sub summa1()
        For n As Integer = 1 To k Step 1
            sum = sum + Math.Cos(n * b * x)
        Next
    End Sub
    Sub summay()
        If (x > 0) Then
            summa1()
            y = Math.Sin(a * x) + sum
        Else
            For n As Integer = j To k Step 1
                sum = sum + Math.Sin(n * a * x)
            Next
            y = Math.Sin(b * x) + sum
        End If
    End Sub
    Sub vvod()
        Console.WriteLine("Введите a,b,k,x,j")
        Dim a As Double = CDbl(Console.ReadLine()),
            b As Double = CDbl(Console.ReadLine()),
            k As Double = CDbl(Console.ReadLine()),
            x As Double = CDbl(Console.ReadLine()),
            j As Integer = CInt(Console.ReadLine())
    End Sub
    Sub vyvod()
        WriteLine(y)
        ReadKey()
    End Sub
    Sub Main()
        vvod()
        summay()
        vyvod()
    End Sub
End Module