Chapter 2.4, Problem 61AYU

First-class mail In $2014$ the U.S Postal Service charged $\$0.98$ postage for first-class mail retail flats (such as an $8.5"$ by $11"$ envelope) weighing up to 1 ounce, plus $\$0.21$ for each additional ounce up to 13 ounces. First-class rates do not apply to flats more than $13$ ounces. Develop a model that relates $C$, the first-class postage charged, for a flat weighing $x$ ounces. Graph the function.