In which months of the calendar year do U.S. gasoline service stations typically have their lowest retail sales levels? In which months of the calendar year do the service stations typically have their highest retail sales levels? Create time series graphs for the monthly data in the file S02_26.xlsx to respond to these two questions. There are really two series, one of actual values and one of seasonally adjusted values. The latter adjusts for any possible seasonality, such as higher values in June and lower values in January, so that any trends are more apparent.