Table 1 gives the retail sales of electricity (in billions of kilowatt-hours) for the residential and commercial sectors in the United States.

(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.

(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.

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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