18. There are some diligent, but unsuccessful, students.
19. Some students are diligent.
[See pp. 60, 1]
3. Half of Smaller Diagram.
Symbols to be interpreted.
__________
-----------
| | |
| x |
| | |
--y-----y'-
__________
------- -------
| | | | | |
1. | | 0 | 2. | 0 | 0 |
| | | | | |
------- -------
------- -------
| | | | | |
3. | - | 4. | 0 | 1 |
| | | | | |
------- -------