Python: A clerk works in a store where the cost of each item is a positive integer number of dollars. For example, something might cost $21, but nothing costs $9.99. In order to make change a clerk has an unbounded number of bills in each of the following face values in dollars: 1, 2, 5, 10, and 20. Write a Python function that takes two arguments, the cost of an item and the amount paid. The function prints how to make change using the smallest possible number of bills.