def _lsqfun_DAA03(massAcid, H, massSample, concAcid, f, AT, concTotals,
    eqConstants):
    """DAA03 Eqs. (14) and (15)."""
    Z = 1 + concTotals['S'] / eqConstants['S']
    return AT + concTotals['S'] / (1 + eqConstants['S'] * Z / (f * H)
        ) + concTotals['F'] / (1 + eqConstants['F'] / (f * H)) + (massSample +
        massAcid) / massSample * f * H / Z - massAcid * concAcid / massSample
