Answer: I would say because he choose 5 for each in stead of just choosing 5 period for both of them so they can listen to both instead of just having 5 listening to CLASSIC and a different 5 listening to OCEAN music, another problem is the amount of people he choose is uneven it should be even so that if it is 5 well there wasnt another student to change it if it is even then there could be like 3 for OCEAN music and maybe 2 for CLASSIC music if it ends out 3 for both just add 2 more kids.
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I Hope this helped. :)