2 A bag contains 5 black discs and 3 red discs. A disc is selected at random from the bag. If it is red it is replaced in the bag. If it is black, it is not replaced. A second disc is now selected at random from the bag.
Find the probability that
- the second disc is black, given that the first disc was black,
- the second disc is black,
- the two discs are of different colours.