Answer:
Out of the 256 syllogisms there are only 24 that are valid. Here are the valid syllogisms AAA-1, AAI-1, AAI-3, AAI-4, AEE-2, AEE-4, AEO-2, AEO-4, AII-1, AII-3, AOO-2, EAE-1, EAE-2, EAO-1, EAO-2, EAO-3, EAO-4, EIO-1, EIO-2, EIO-3, EIO-4, IAI-3, IAI-4, and OAO-3.