B grade: { 18, 22, 26, 30, 35, 36, 37, 39, 40, 41, 43, 44, 45, 47, 48, 49 }
C grade: { 19, 20, 21, 23, 24, 25, 27, 28, 29, 31, 32, 33 }
F grade: { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72 }