mu 1 2 11A mu 11A 2 19ABC mu 11A 19ABC 20AB mu 20AB 2 12A mu 11A 20AB 3 mu 3 19ABC 31AB mu 12A 3 28AB mu 3 28AB 16AB mu 19ABC 16AB 16CD mu 12A 16CD 7B mu 7B 28AB 15AB oup 10 7B 11A 12A 15AB 16AB 16CD 19ABC 20AB 28AB 31AB echo "Classes 7B 11A 12A 15A-B 16A-B 16C-D 19A-C 20A-B 28A-B 31A-B"