 q_15   |    0.        1         1         1         1    |
|         |         |                                                 |
|  p_4    |  q_17   |    1.        0         0         0         1    |
|         |         |                                                 |
|  p_5    |  q_19   |    1.        0         0         1         1    |
|         |         |                                                 |
|  p_6    |  q_21   |    1.        0         1         0         1    |
|         |         