A bag contains six balls numbered 1 to 6. A ball is drawn at random and its number noted. The ball is then returned to the bag. The numbers for the first 30 draws are:

                    

Number	Frequency
1	4
2	5
3	3
4	n
5	6
6	5

Write down the value of n.

 b Calculate the mean number.

 c Write down the model number.