Solution to 4.
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| T | T | T | F | F | T | T |
| T | T | F | F | F | F | F |
| T | F | T | F | F | T | T |
| T | F | F | F | F | F | T |
| F | T | T | T | T | T | T |
| F | T | F | T | T | T | T |
| F | F | T | T | F | T | T |
| F | F | F | T | F | T | T |
This argument is not valid, as can be seen from row six, in which all premises (bold) are true, but the conclusion (italic) is false.