def gc(coeff, mag):
    """
    Returns the set of coefficients to be used for the calculation of GM
    as a function of earthquake magnitude

    :param coeff:
        A dictionary of parameters for the selected IMT
    :param mag:
        Magnitude value
    :returns:
        The set of coefficients
    """
    if mag > 6.5:
        a1ca = coeff['ua']
        a1cb = coeff['ub']
        a1cc = coeff['uc']
        a1cd = coeff['ud']
        a1ce = coeff['ue']
        a2ca = coeff['ia']
        a2cb = coeff['ib']
        a2cc = coeff['ic']
        a2cd = coeff['id']
        a2ce = coeff['ie']
    else:
        a1ca = coeff['a']
        a1cb = coeff['b']
        a1cc = coeff['c']
        a1cd = coeff['d']
        a1ce = coeff['e']
        a2ca = coeff['ma']
        a2cb = coeff['mb']
        a2cc = coeff['mc']
        a2cd = coeff['md']
        a2ce = coeff['me']
    return a1ca, a1cb, a1cc, a1cd, a1ce, a2ca, a2cb, a2cc, a2cd, a2ce
