def ql(fmp, fs, f0p):
    """Calculate qL

    qL = ((fmp - fs) / (fmp - f0p)) * (f0p / fs)

    :param fmp: Fm'
    :param fs: Fs
    :param f0p: F0'
    :returns: qL (float)
    """

    return ((fmp - fs) / (fmp - f0p)) * (f0p / fs)