5 Maryam has 7 sweets in a tin; 6 are toffees and 1 is a chocolate. She chooses one sweet at random and takes it out. Her friend adds 3 chocolates to the tin. Then Maryam takes another sweet at random out of the tin.
- Draw a fully labelled tree diagram to illustrate this situation.
- Draw up the probability distribution table for the number of toffees taken.
- Find the mean number of toffees taken.
- Find the probability that the first sweet taken is a chocolate, given that the second sweet taken is a toffee.