A   B   C   D
  +----------------
1 | 6 | 6 |5.8| ? |
  |---+---+---+---+
2 | 6 | 6 |5.8| ? |
  |---+---+---+---+
3 |5.8|5.8| ? | ? |
  |---+---+---+---+
4 | ? | ? | ? | ? |
  |---+---+---+---+