@staticmethod
def v3_ps(p, s):
    """function v3_ps = v3_ps(p, s)

        Revised Supplementary Release on Backward Equations for the functions T(p, h), v(p, h) and T(p, s), v(p, s) for Region 3 of the IAPWS Industrial formulation 1997 for the Thermodynamic Properties of Water and Steam 2004

        3.4 Backward Equations T(p, s) and v(p, s) for Subregions 3a and 3b

        Boundary equation, Eq 6 Page 11
        """
    if s <= 4.41202148223476:
        Ii = [-12, -12, -12, -10, -10, -10, -10, -8, -8, -8, -8, -6, -5, -4,
            -3, -3, -2, -2, -1, -1, 0, 0, 0, 1, 2, 4, 5, 6]
        Ji = [10, 12, 14, 4, 8, 10, 20, 5, 6, 14, 16, 28, 1, 5, 2, 4, 3, 8,
            1, 2, 0, 1, 3, 0, 0, 2, 2, 0]
        ni = [79.5544074093975, -2382.6124298459, 17681.3100617787, -
            0.00110524727080379, -15.3213833655326, 297.544599376982, -
            35031520.6871242, 0.277513761062119, -0.523964271036888, -
            148011.182995403, 1600148.99374266, 1708023226634.27, 
            0.000246866996006494, 1.6532608479798, -0.118008384666987, 
            2.537986423559, 0.965127704669424, -28.2172420532826, 
            0.203224612353823, 1.10648186063513, 0.52612794845128, 
            0.277000018736321, 1.08153340501132, -0.0744127885357893, 
            0.0164094443541384, -0.0680468275301065, 0.025798857610164, -
            0.000145749861944416]
        Pi = p / 100
        Sigma = s / 4.4
        omega = 0
        for i in range(0, 28):
            omega = omega + ni[i] * (Pi + 0.187) ** Ii[i] * (Sigma - 0.755
                ) ** Ji[i]
        v3_ps = omega * 0.0028
    else:
        Ii = [-12, -12, -12, -12, -12, -12, -10, -10, -10, -10, -8, -5, -5,
            -5, -4, -4, -4, -4, -3, -2, -2, -2, -2, -2, -2, 0, 0, 0, 1, 1, 2]
        Ji = [0, 1, 2, 3, 5, 6, 0, 1, 2, 4, 0, 1, 2, 3, 0, 1, 2, 3, 1, 0, 1,
            2, 3, 4, 12, 0, 1, 2, 0, 2, 2]
        ni = [5.91599780322238e-05, -0.00185465997137856, 
            0.0104190510480013, 0.0059864730203859, -0.771391189901699, 
            1.72549765557036, -0.000467076079846526, 0.0134533823384439, -
            0.0808094336805495, 0.508139374365767, 0.00128584643361683, -
            1.63899353915435, 5.86938199318063, -2.92466667918613, -
            0.00614076301499537, 5.76199014049172, -12.1613320606788, 
            1.67637540957944, -7.44135838773463, 0.0378168091437659, 
            4.01432203027688, 16.0279837479185, 3.17848779347728, -
            3.58362310304853, -1159952.60446827, 0.199256573577909, -
            0.122270624794624, -19.1449143716586, -0.0150448002905284, 
            14.6407900162154, -3.2747778718823]
        Pi = p / 100
        Sigma = s / 5.3
        omega = 0
        for i in range(0, 31):
            omega = omega + ni[i] * (Pi + 0.298) ** Ii[i] * (Sigma - 0.816
                ) ** Ji[i]
        v3_ps = omega * 0.0088
    return v3_ps
