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If 20 C 1 + (2 2 ) 20 C 2 + (3 2 ) 20 C 3 + ..... + (20 2 ) 20 C 20 = A(2 β ), then the ordered pair (A, β ) is equal to :

1. (420, 19)
2. (420, 18)
3. (380, 18)
4. (380, 19)

Correct answer: (420, 18)

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