Please help!
A box contains 8 ginger biscuits and 7 oat biscuits. Mathew chooses a biscuit at random. If it is a ginger biscuit, he puts it back. If it is an oat biscuit, he eats it. In either case, he then chooses a second biscuit. Again, if it is a ginger biscuit, he puts it back and if it is an oat biscuit, he eats it. He makes a third selection, with the same outcomes. Draw a tree diagram and find the probability that Mathew eats exactly two oat biscuits.
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