def _Backward2c_T_Ps(P, s):
    """Backward equation for region 2c, T=f(P,s)

    Parameters
    ----------
    P : float
        Pressure, [MPa]
    s : float
        Specific entropy, [kJ/kgK]

    Returns
    -------
    T : float
        Temperature, [K]

    References
    ----------
    IAPWS, Revised Release on the IAPWS Industrial Formulation 1997 for the
    Thermodynamic Properties of Water and Steam August 2007,
    http://www.iapws.org/relguide/IF97-Rev.html, Eq 27

    Examples
    --------
    >>> _Backward2c_T_Ps(20,5.75)
    697.992849
    >>> _Backward2c_T_Ps(80,5.75)
    949.017998
    """
    I = [-2, -2, -1, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 3, 3, 3, 4, 4, 4, 5, 
        5, 5, 6, 6, 7, 7, 7, 7, 7]
    J = [0, 1, 0, 0, 1, 2, 3, 0, 1, 3, 4, 0, 1, 2, 0, 1, 5, 0, 1, 4, 0, 1, 
        2, 0, 1, 0, 1, 3, 4, 5]
    n = [909.68501005365, 2404.566708842, -591.6232638713, 541.45404128074,
        -270.98308411192, 979.76525097926, -469.66772959435, 
        14.399274604723, -19.104204230429, 5.3299167111971, -
        21.252975375934, -0.3114733441376, 0.60334840894623, -
        0.042764839702509, 0.0058185597255259, -0.014597008284753, 
        0.0056631175631027, -7.6155864584577e-05, 0.00022440342919332, -
        1.2561095013413e-05, 6.3323132660934e-07, -2.0541989675375e-06, 
        3.6405370390082e-08, -2.9759897789215e-09, 1.0136618529763e-08, 
        5.9925719692351e-12, -2.0677870105164e-11, -2.0874278181886e-11, 
        1.0162166825089e-10, -1.6429828281347e-10]
    Pr = P / 1
    sigma = s / 2.9251
    T = 0
    for i, j, ni in zip(I, J, n):
        T += ni * Pr ** i * (2 - sigma) ** j
    return T
