Let a bag contains 15 balls in which the balls can have either black colour or white colour. If Bn is the event that bag contains exactly n black balls and its probability is proportional to n² and E is the event of getting a black ball when a ball is drawn randomly from the bag, then:

(a) _n=0¹⁵ P(B_n) = 1

(b) P(E) = 24/31

(c) P(B₅/E) = 5/376

(d) P(B₅/E) = 5/576

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