Electronic Sales (2000s) Annual U.S. factory sales of consumer electronics goods to...

Electronic Sales (2000s) Annual U.S. factory sales of consumer electronics goods to dealers from 2000 through 2009 can be modeled as

where output is measured in billion dollars and t is the number of years since 2000.

(Sources: Based on data from Statistical Abstract, 2009; and Consumer Electronics Association)

a. Numerically estimate to the nearest tenth the derivative of S when t = 8.

b. Interpret the answer to part a.