11.give that : P(A)=P(B)=P(C)=1/4,P(A∩B)=P(C∩B)=0 and P(A∩C)=1/8 ,compute the probability that at least one of the three events A,B or C will occur .

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12 . suppose that :P(A)=0.4 , P(B)=α,P(AUB)= 0.7:

i.what is the value of αwhich makes A and B disjoint ?

ii. what is the value of αwhich makes A and B independent ?

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13 . show that:

i.P(A∩B∩C)=P(A|B∩C)P(B|C)P(C)