$\"\"$

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The combination is $\"\"$ .

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The combinations formula is $\"\"$ .

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$\"\"$ (Apply combinations formula)

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$\"\"$ ( $\"\"$ ) $\"\"$

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$\"\"$ (Expand $\"\"$ )

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$\"\"$ (Cancel common terms) \ \

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$\"\"$ . (Multiply: $\"\"$ ) $\"\"$

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The total number of combinations are 6435.