Chapter 1.4, Problem 60AYU

Minimum Payments for Credit Cards Holders of a credit cards issued by banks, department stores, oil companies, and so on, receive bills each month that state minimum amounts that must be paid by a certain due date. The minimum due depends on the total amount owed. One such credit card company uses the following rules: For a bill of less than $10, the entire amount is due. For a bill of at least $\$10$ but less than $\$500,$ the minimum due is $10. A minimum of $30 is due on a bill of at least $500 but less than $1000, a minimum of $50 is due on a bill of at least $1000 but less than $1500, and a minimum of $70 is due on bills of $1500 or more. Find the function $f$ that describes the minimum payments due on a bill of $x$ dollars. Graph $f$.