Natural-gas consumption. The data in Table 1 give the U.S. consumption of natural gas in t...

Natural-gas consumption. The data in Table 1 give the U.S. consumption of natural gas in trillions of cubic feet.

Table 1

(A) Let x represent time (in years), with x = 0 corresponding to 1960, and let y represent the corresponding U.S. consumption of natural gas. Enter the data set in a graphing calculator and find a cubic regression equation for the data.

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(B) If y = N(x) denotes the regression equation found in part (A), find N(60) and N′(60), and write a brief verbal interpretation of these results.