Question 1141833
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First, I checked that the given sequence P(0), P(1), P(2), P(3), P(4), P(5), P(6), P(7) of 8 terms monotonically increases 
and that the sum of all 8 (eight) given probabilities in the post is equal to 1 :


    0.001 + 0.006 + 0.022 + 0.052 + 0.091+ 0.128 + 0.149 + 0.551 = 1,


so the given data makes sense.



Second, the answer to the question is the sum of the last 5 (five) terms of the sequence


    P(the number of phone calls is at least 3) = P(3) +  P(4)  + P(5)  + P(6)  + P(7) = 

                                               = 0.052 + 0.091 + 0.128 + 0.149 + 0.551 = 0.971.      <U>ANSWER</U>
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