Paragraph for Questions 11 and 12
A box B1 contains 1 white ball, 3 red balls and 2 black balls. Another box B2 contains 2 white balls, 3 red balls and 4 black balls. A third box B3 contains 3 white balls, 4 red balls and 5 black balls.
If one ball is drawn from each of the boxes B1, B2 and B3, the probability that all three drawn balls are of the same colour is