4. Student A: During the period 2000-2015, the sales of cheesecake at
Jenna's Cheesecake Company increased by 800 per year. In 2003, Jenna
sold 3,620 cheesecakes. Write an equation that gives the annual sales as a
function of the number of years since 2000. What was the number of
cheesecakes sold in 2015?