3 A pack of 40 cards consists of 10 cards in each of four colours: red, yellow, blue and green. The pack is dealt at random into four "hands", each of 10 cards. The hands are labelled North, South, East and West.
- Find the probability that West has exactly 3 red cards.
- Find the probability that West has exactly 3 red cards, given that East and West have between them a total of exactly 5 red cards.
- South has 5 red cards and 5 blue cards. These cards are placed in a row in a random order. Find the probability that the colour of each card is different from the colour of the preceding card.