Urn A contains 9 cubes of which 4 are red. Urn B contains 5 cubes of which 2 are red. A cube is drawn at random and in succession from each urn.
a) Draw a tree diagram representing this process.
b) Find the probability that both cubes are red.
c) Find the probability that only 1 cube is red.
d) If only 1 cube is red, find the probability that it came from urn A.