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1-1: Two. The Computing courses must use red. Math and English can not share a colour, so one of the blue is for general notes. This leaves a choice between English using blue and Math green or vice versa.
1-2: Zero. The Computing courses must take all of one colour and one of another. The second of the second colour can not be for a second subject so it must be for general notes. this leaves the third colour for Math and English which is not allowed.
2-1: Again, the Computer courses must use red. The other two courses plus general notes can be allocated in any way. There are three possibilities: blue for any two of the three and green for the third. (Remember that binders of each colour are not distinct, so there are not six possibilities.)
2-2: Zero. There are three Computing courses and not enough of any colour so that the Computing courses use only one colour.