Chapter 2.4, Problem 87E

Electricity consumption. Table 1 gives the retail sales of electricity (in billions of kilowatt-hours) for the residential and commercial sectors in the United States. (Source: Energy Information Administration)

Table 1 Electricity Sales

Year	Residential	Commercial
2000	1,192	1,055
2003	1,276	1,199
2006	1,352	1,300
2009	1,365	1,307
2012	1,375	1,327
2015	1,400	1,358

1. (A) Let x represent time (in years) with x = 0 corresponding to 2000, and let y represent the corresponding residential sales. Enter the appropriate data set in a graphing calculator and find a quadratic regression equation for the data.
2. (B) If y = R(x) denotes the regression equation found in part (A), find R(30) and R′(30), and write a brief verbal interpretation of these results. Round answers to the nearest tenth of a billion.