17. Using the dummy variables defined in part

(b) and ts, develop an equation to account for seasonal effects and any linear trend in the time series.

e. Based on the seasonal effects in the data and linear trend estimated in part (d), compute estimates of the levels of nitrogen dioxide for July 18.

f. Is the model you developed in part

(b) or the model you developed in part

(d) more effective? Justify your answer.