Function ARate(nper, pmt, pv, fv, typ, guess) As Double
    ' Solve for the amortization rate
    ' Invert an of i and return i
    f0 = 2
    ep = 0.0000001
    i0 = 0#
    i1 = guess
    If i1 = 0# Then
        i1 = 5# / 100
    End If
    am = (1 - Exp(-nper * Log(1 + i1))) / (nper * i1) + fv * Exp(-nper * Log(1 + i1)) / nper + fv * Exp(-nper * Log(1 + i1)) / nper
    am = am * (1 + typ * i1)
    an = pv / (nper * pmt)
    ' Determine bounds
    While (am > an)
        i1 = i1 * f0
        am = (1 - Exp(-nper * Log(1 + i1))) / (nper * i1) + fv * Exp(-nper * Log(1 + i1)) / nper + fv * Exp(-nper * Log(1 + i1)) / nper
        am = am * (1 + typ * i1)
    Wend
    While (am < an)
        i1 = i1 / f0
        am = (1 - Exp(-nper * Log(1 + i1))) / (nper * i1) + fv * Exp(-nper * Log(1 + i1)) / nper
        am = am * (1 + typ * i1)
    Wend
    ' Bisection
    i0 = i1
    i1 = (i0 + i0 * f0) / 2
    i2 = i0 * f0
    am = (1 - Exp(-nper * Math.Log(1 + i1))) / (nper * i1) + fv * Exp(-nper * Log(1 + i1)) / nper
    am = am * (1 + typ * i1)
    While (Abs(am - an) > ep)
        'am = (1 - Exp(-nper * Math.Log(1 + i1))) / (nper * i1) + fv * Exp(-nper * Log(1 + i1)) / nper
        'am = am * (1 + typ * i1)
        If (am > an) Then
            i0 = i1
            i1 = (i1 + i2) / 2
        Else
            i2 = i1
            i1 = (i0 + i1) / 2
        End If
        am0 = am
        am = (1 - Exp(-nper * Log(1 + i1))) / (nper * i1) + fv * Exp(-nper * Log(1 + i1)) / nper
        am = am * (1 + typ * i1)
        ' Unable to converge?
        If am = am0 Then
            am = an
        End If
   Wend
    ARate = i1
End Function
Function SRate(nper, pmt, pv, fv, typ, guess) As Double
    ' Solve for the sinking fund rate
    ' Invert sn of i and return i
    f0 = 2
    ep = 0.0000001
    i0 = 0#
    i1 = guess
    If i1 = 0# Then
        i1 = 5# / 100
    End If
    am = (Exp(nper * Log(1 + i1)) - 1) / (nper * i1) + fv / nper
    am = am * (1 + typ * i1)
    an = pv / (nper * pmt)
    ' Determine bounds
    While (am < an)
        i1 = i1 * f0
        am = (Exp(nper * Log(1 + i1)) - 1) / (nper * i1) + fv / nper
        am = am * (1 + typ * i1)
    Wend
    While (am > an)
        i1 = i1 / f0
        am = (Exp(nper * Log(1 + i1)) - 1) / (nper * i1) + fv / nper
        am = am * (1 + typ * i1)
    Wend
    ' Bisection
    i0 = i1
    i1 = (i0 + i0 * f0) / 2
    i2 = i0 * f0
    am = (Exp(nper * Log(1 + i1)) - 1) / (nper * i1) + fv / nper
    am = am * (1 + typ * i1)
    While (Abs(am - an) > ep)
        'am = (Exp(nper * Log(1 + i1)) - 1) / (nper * i1) + fv / nper
        'am = am * (1 + typ * i1)
        If (am < an) Then
            i0 = i1
            i1 = (i1 + i2) / 2
        Else
            i2 = i1
            i1 = (i0 + i1) / 2
        End If
        am0 = am
        am = (Exp(nper * Log(1 + i1)) - 1) / (nper * i1) + fv / nper
        am = am * (1 + typ * i1)
        ' Unable to converge?
        If am = am0 Then
            am = an
        End If
   Wend
    SRate = i1
End Function