def extrapolate_correlation(correlation_energies, cardinals, beta):
    """Extrapolates the correlation energy.

    For more information, see Equation 2 in DOI: 10.1021/ct100396y.

    Parameters
    ----------
    correlation_energies : :obj:`tuple` (:obj:`float`)
        The small (X) to large (Y) basis set correlation energies, respectively.
    cardinals : :obj:`tuple`
        The X and Y cardinal numbers of the basis sets, respectively.
    beta : :obj:`float`
        The basis-set dependent constant beta.
    
    Returns
    -------
    :obj:`float`
        Extrapolated correlation energy.
    """
    correlation_x, correlation_y = correlation_energies
    cardinal_x, cardinal_y = cardinals
    numerator = (cardinal_x**beta * correlation_x) - (cardinal_y**beta * correlation_y)
    denominator = cardinal_x**beta - cardinal_y**beta
    cbs_correlation = numerator / denominator
    return cbs_correlation