def _compute_term_3_4(self, dists, C):
        """
        Compute term 3 and 4 in equation 1 page 1.
        """
        cutoff = 6.056877878
        rhypo = dists.rhypo.copy()
        rhypo[rhypo <= cutoff] = cutoff
        return C['c3'] * np.log(rhypo) + C['c4'] * rhypo