Answer:
The amount owed is $10.51, and we want to provide this amount by using the smallest number of bills and coins possible.
If we want to do it, we must use the biggest bill possible until the amount is reached.
Meaning, you could only give a bill of $20 and it would be solved, but there are another way more efficient.
You can use a $10 bill, and you can see that there are $0.51 left.
The next smallest bill is $5, and in this case, you will be passing for $4.49, so this option can be discarded.
The next option is $1, and in this case, you only are passing by $0.49, so it is not so bad.
Then the correct way (The most efficient one) is to give a $10 bill and $1 coin/bill
