def METHOD_NAME(sites, c4, c5, c6, c7):
    """
    Returns the distance scaling term
    """
    return (c4 * np.log10(sites.slope) +
            c5 * np.log10(sites.T_15) +
            c6 * np.log10(100 - sites.F_15) +
            c7 * np.log10(sites.D50_15 + 0.1))