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If the probability that the random variable X takes values x is given by P(X = x) = k(x + 1)3 –x , x = 0, 1, 2, 3, ........., where k is a constant, the P(X ≥ 2) is equal to

1. 27 7
2. 18 7
3. 18 11
4. 27 20

Correct answer: 27 7

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