Averages

Imagine you have a large supply of 3kg and 8kg weights.
How many of each weight would you need for the average (mean) of the weights to be 4kg?
How many of each weight would you need for the average (mean) of the weights to be 6kg?
If you had other combinations of the 3kg and 8kg weights, what other whole number averages could you make?
What's the smallest?
What's the largest?
Can you make all the whole number values in between?