First function:

We will make a small diavola pizza
We will make a large quatro formaggio pizza
We will make a family-size artichoke pizza


Second function (with defaults):

We will make a large pepperoni pizza
We will make a small diavola pizza
We will make a large quatro formaggio pizza
We will make a family-size artichoke pizza


Third function (with averages):

The average of [10, 20, 30, 40, 50] is 30.0


Fourth function (with averages and check for []):

The average of [10, 20, 30, 40, 50] is 30.0
The list is empty!
The average of [] is None


Fifth function same as the fourth:

The average of [10, 20, 30, 40, 50] is 30.0