U.S. Postal Service first-class mail volume was 91.7 billion pieces in 2008, and it decreased by about 4.9 billion pieces per year for the period 2008€“2013.
a. Complete Table 39 to help find an expression that stands for the U.S. Postal Service first-class mail volume (in billions of pieces) in the year that is t years since 2008. Show the arithmetic to help you see a pattern.

b. Evaluate the expression that you found in part (a) for t = 5. What does your result mean in this situation?

Table 39 U.S. Postal Service First-Class Mail Volume Years since 2008 First-Class Mail Volume (billions of pieces)