def _Backward3_P_hs(h, s):
    """Backward equation for region 3, P=f(h,s)

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

    Returns
    -------
    P : float
        Pressure, [MPa]
    """
    sc = 4.41202148223476
    if s <= sc:
        return _Backward3a_P_hs(h, s)
    else:
        return _Backward3b_P_hs(h, s)