def _Backward2_T_Ps(P, s):
    """Backward equation for region 2, T=f(P,s)

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

    Returns
    -------
    T : float
        Temperature, [K]
    """
    if P <= 4:
        T = _Backward2a_T_Ps(P, s)
    elif s >= 5.85:
        T = _Backward2b_T_Ps(P, s)
    else:
        T = _Backward2c_T_Ps(P, s)

    if P <= 22.064:
        Tsat = _TSat_P(P)
        T = max(Tsat, T)
    return T