Annual sales of echinacea were $132 million in 2009 and de- creased by about $6.9 million per year until 2014. Let f(t) be the annual echinacea sales (in millions of dollars) at t years since 2009.
a. Find an equation of f.
b. What is the slope? What does it mean in this situation?
c. Find f (3) - f (2). Compare the result with the slope. Why does your comparison make sense?
d. Estimate the sales of echinacea in 2013.
e. Estimate the mean sales of echinacea per state in 2014. Is your result likely an underestimate or an overestimate for California, which is the state with the largest population?