8、 The collection efficiency of a cyclone is 45% over the size range 0-5 mm, 80% over the size 96% for particles exceeding 10 mm. Calculate the total efficiency of collection for the following dust: 50% 0-5 mm, 30% 5-10 mm, 20% above 10 mm.
(A) 86%
(B) 71%
(C) 53%
(D) 65.7%

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統計： A(0), B(0), C(1), D(2), E(0) #872683