def _h2c3b_s(s):
    """Define the saturated line boundary between Region 4 and 2c-3b, h=f(s)

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

    Returns
    -------
    h : float
        Specific enthalpy, [kJ/kg]

    Notes
    ------
    Raise :class:`NotImplementedError` if input isn't in limit:

        * sc ≤ s ≤ 5.85

    References
    ----------
    IAPWS, Revised Supplementary Release on Backward Equations p(h,s) for
    Region 3, Equations as a Function of h and s for the Region Boundaries, and
    an Equation Tsat(h,s) for Region 4 of the IAPWS Industrial Formulation 1997
    for the Thermodynamic Properties of Water and Steam,
    http://www.iapws.org/relguide/Supp-phs3-2014.pdf. Eq 6

    Examples
    --------
    >>> _h2c3b_s(5.5)
    2687.693850
    >>> _h2c3b_s(4.5)
    2144.360448
    """
    if s < 4.41202148223476 or s > 5.85:
        raise NotImplementedError('Incoming out of bound')
    sigma = s / 5.9
    I = [0, 0, 0, 1, 1, 5, 6, 7, 8, 8, 12, 16, 22, 22, 24, 36]
    J = [0, 3, 4, 0, 12, 36, 12, 16, 2, 20, 32, 36, 2, 32, 7, 20]
    n = [1.04351280732769, -2.27807912708513, 1.80535256723202, 
        0.420440834792042, -105721.24483466, 4.36911607493884e+24, -
        328032702839.753, -6786867608042700.0, 7439.57464645363, -
        3.56896445355761e+19, 1.67590585186801e+31, -3.55028625419105e+37, 
        396611982166.538, -4.14716268484468e+40, 3.59080103867382e+18, -
        1.16994334851995e+40]
    suma = 0
    for i, j, ni in zip(I, J, n):
        suma += ni * (sigma - 1.02) ** i * (sigma - 0.726) ** j
    return 2800 * suma ** 4
