A, 13, 14, 15, 16, 17, 18, 19, 20 B, 24, 23, 22, 21, 20, 19, 18, 17...

Bài 1: a, 13, 14, 15, 16, 17, 18, 19, 20 b, 24, 23, 22, 21, 20, 19, 18, 17