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A bag contain blue, green and red pens of the same type in the ratio 8:2:5 respectively. A pen is picked at random without replacement, and its colour noted.
(a) Determine the probability that the first pen picked is
(i) Blue
(ii) Either green or red
(b) Using a tree diagram determine the probability that
(i)the first two pens picked are both green
(ii)only one of the first two pens picked is red.