def _h3a_s(s):
    """Define the saturated line boundary between Region 4 and 3a, h=f(s)
    
    >>> "%.6f" % _h3a_s(3.8)
    '1685.025565'
    >>> "%.6f" % _h3a_s(4.2)
    '1949.352563'
    """
    sigma=s/3.8
    I=[0, 0, 0, 0, 2, 3, 4, 4, 5, 5, 6, 7, 7, 7, 10, 10, 10, 32, 32]
    J=[1, 4, 10, 16, 1, 36, 3, 16, 20, 36, 4, 2, 28, 32, 14, 32, 36, 0, 6]
    n=[0.822673364673336, 0.181977213534479, -0.112000260313624e-1, -0.746778287048033e-3, -0.179046263257381, 0.424220110836657e-1, -0.341355823438768, -0.209881740853565e1, -0.822477343323596e1, -0.499684082076008e1, 0.191413958471069, 0.581062241093136e-1, -0.165505498701029e4, 0.158870443421201e4, -0.850623535172818e2, -0.317714386511207e5, -0.945890406632871e5, -0.139273847088690e-5, 0.631052532240980]
    
    suma=0
    for i in range(19):
        suma+=n[i]*(sigma-1.09)**I[i]*(sigma+0.366e-4)**J[i]
    return 1700*suma