code: def _Backward2_P_hs(h, s):
      
      sfbc = 5.85
      hamin = _hab_s(s)
      if h <= hamin:
          P = _Backward2a_P_hs(h, s)
      elif s >= sfbc:
          P = _Backward2b_P_hs(h, s)
      else:
          P = _Backward2c_P_hs(h, s)
      return P
docs: Backward equation for region 2, P=f(h,s)
  
      Parameters
      ----------
      h : float
          Specific enthalpy, [kJ/kg]
      s : float
          Specific entropy, [kJ/kgK]
  
      Returns
      -------
      P : float
          Pressure, [MPa]