@staticmethod
def T2_ps(p, s):
    """function T2_ps = T2_ps(p, s)

        6 Equations for Region 2,6.3.2 The Backward Equations T( p, s ) for Subregions 2a, 2b, and 2c

        Page 26
        """
    if p < 4:
        sub_reg = 1
    elif s < 5.85:
        sub_reg = 3
    else:
        sub_reg = 2
    if sub_reg == 1:
        Ii = [-1.5, -1.5, -1.5, -1.5, -1.5, -1.5, -1.25, -1.25, -1.25, -1, 
            -1, -1, -1, -1, -1, -0.75, -0.75, -0.5, -0.5, -0.5, -0.5, -0.25,
            -0.25, -0.25, -0.25, 0.25, 0.25, 0.25, 0.25, 0.5, 0.5, 0.5, 0.5,
            0.5, 0.5, 0.5, 0.75, 0.75, 0.75, 0.75, 1, 1, 1.25, 1.25, 1.5, 1.5]
        Ji = [-24, -23, -19, -13, -11, -10, -19, -15, -6, -26, -21, -17, -
            16, -9, -8, -15, -14, -26, -13, -9, -7, -27, -25, -11, -6, 1, 4,
            8, 11, 0, 1, 5, 6, 10, 14, 16, 0, 4, 9, 17, 7, 18, 3, 15, 5, 18]
        ni = [-392359.83861984, 515265.7382727, 40482.443161048, -
            321.93790923902, 96.961424218694, -22.867846371773, -
            449429.14124357, -5011.8336020166, 0.35684463560015, 
            44235.33584819, -13673.388811708, 421632.60207864, 
            22516.925837475, 474.42144865646, -149.31130797647, -
            197811.26320452, -23554.39947076, -19070.616302076, 
            55375.669883164, 3829.3691437363, -603.91860580567, 
            1936.3102620331, 4266.064369861, -5978.0638872718, -
            704.01463926862, 338.36784107553, 20.862786635187, 
            0.033834172656196, -4.3124428414893e-05, 166.53791356412, -
            139.86292055898, -0.78849547999872, 0.072132411753872, -
            0.0059754839398283, -1.2141358953904e-05, 2.3227096733871e-07, 
            -10.538463566194, 2.0718925496502, -0.072193155260427, 
            2.074988708112e-07, -0.018340657911379, 2.9036272348696e-07, 
            0.21037527893619, 0.00025681239729999, -0.012799002933781, -
            8.2198102652018e-06]
        Pi = p
        Sigma = s / 2
        teta = 0
        for i in range(0, 46):
            teta = teta + ni[i] * Pi ** Ii[i] * (Sigma - 2) ** Ji[i]
    elif sub_reg == 2:
        Ii = [-6, -6, -5, -5, -4, -4, -4, -3, -3, -3, -3, -2, -2, -2, -2, -
            1, -1, -1, -1, -1, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 2, 2,
            2, 3, 3, 3, 4, 4, 5, 5, 5]
        Ji = [0, 11, 0, 11, 0, 1, 11, 0, 1, 11, 12, 0, 1, 6, 10, 0, 1, 5, 8,
            9, 0, 1, 2, 4, 5, 6, 9, 0, 1, 2, 3, 7, 8, 0, 1, 5, 0, 1, 3, 0, 
            1, 0, 1, 2]
        ni = [316876.65083497, 20.864175881858, -398593.99803599, -
            21.816058518877, 223697.85194242, -2784.1703445817, 
            9.920743607148, -75197.512299157, 2970.8605951158, -
            3.4406878548526, 0.38815564249115, 17511.29508575, -
            1423.7112854449, 1.0943803364167, 0.89971619308495, -
            3375.9740098958, 471.62885818355, -1.9188241993679, 
            0.41078580492196, -0.33465378172097, 1387.0034777505, -
            406.63326195838, 41.72734715961, 2.1932549434532, -
            1.0320050009077, 0.35882943516703, 0.0052511453726066, 
            12.838916450705, -2.8642437219381, 0.56912683664855, -
            0.099962954584931, -0.0032632037778459, 0.00023320922576723, -
            0.1533480985745, 0.029072288239902, 0.00037534702741167, 
            0.0017296691702411, -0.00038556050844504, -3.5017712292608e-05,
            -1.4566393631492e-05, 5.6420857267269e-06, 4.1286150074605e-08,
            -2.0684671118824e-08, 1.6409393674725e-09]
        Pi = p
        Sigma = s / 0.7853
        teta = 0
        for i in range(0, 44):
            teta = teta + ni[i] * Pi ** Ii[i] * (10 - Sigma) ** Ji[i]
    else:
        Ii = [-2, -2, -1, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 3, 3, 3, 4, 4, 4,
            5, 5, 5, 6, 6, 7, 7, 7, 7, 7]
        Ji = [0, 1, 0, 0, 1, 2, 3, 0, 1, 3, 4, 0, 1, 2, 0, 1, 5, 0, 1, 4, 0,
            1, 2, 0, 1, 0, 1, 3, 4, 5]
        ni = [909.68501005365, 2404.566708842, -591.6232638713, 
            541.45404128074, -270.98308411192, 979.76525097926, -
            469.66772959435, 14.399274604723, -19.104204230429, 
            5.3299167111971, -21.252975375934, -0.3114733441376, 
            0.60334840894623, -0.042764839702509, 0.0058185597255259, -
            0.014597008284753, 0.0056631175631027, -7.6155864584577e-05, 
            0.00022440342919332, -1.2561095013413e-05, 6.3323132660934e-07,
            -2.0541989675375e-06, 3.6405370390082e-08, -2.9759897789215e-09,
            1.0136618529763e-08, 5.9925719692351e-12, -2.0677870105164e-11,
            -2.0874278181886e-11, 1.0162166825089e-10, -1.6429828281347e-10]
        Pi = p
        Sigma = s / 2.9251
        teta = 0
        for i in range(0, 30):
            teta = teta + ni[i] * Pi ** Ii[i] * (2 - Sigma) ** Ji[i]
    return teta
