Question 1072295
So from each class you have nine choices so for the 3 class pick you'd have,
{{{N=9*9*9=729}}} possible picks.
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Why do you have two 11's for each class. 
I'll treat them as separate students but you should change the name to avoid confusion.
Start with Class A, first choice 11A
(11A, CB, CC)
Choose Class B, first choice 11B
(11A, 11B, CC)
Then choose each possible choice in Class C,
(11A,11B,11C)
(11A,11B,22C)
(11A,11B,YYC)
(11A,11B,1YC)
(11A,11B,2YC)
(11A,11B,Y1C)
(11A,11B,Y2C)
(11A,11B,12C)
(11A,11B,11C)
Then move to the next Class B choice, 22B.
(11A,22B,11C)
(11A,22B,22C)
(11A,22B,YYC)
(11A,22B,1YC)
(11A,22B,2YC)
(11A,22B,Y1C)
(11A,22B,Y2C)
(11A,22B,12C)
(11A,22B,11C)
Once you exhaust all the B choices then increment on A and start all over again,
As an example,
(22A,11B,11C)
(22A,11B,22C)
(22A,11B,YYC)
(22A,11B,1YC)
(22A,11B,2YC)
(22A,11B,Y1C)
(22A,11B,Y2C)
(22A,11B,12C)
(22A,11B,11C)
Keep going this way until you have 729 picks made.