def formula(foyer_fiscal, period, parameters):
    """
        Impôt sans quotient familial
        """
    rni = foyer_fiscal('rni', period)
    nb_adult = foyer_fiscal('nb_adult', period)
    bareme = parameters(period).impot_revenu.bareme
    A = bareme.calc(rni / nb_adult)
    return nb_adult * A
