Given $1, $5, $20, and $100 dollar bills, what is the fewest number of bills needed to form amounts ranging from $1 to $100? (eg. $4 would need four $1 dollar bills) You can reuse bills so the number of bills is not cumulative. What is the fewest amount of bills you need to always have exact change for a transaction of $x and $(100-x) given that x<100?