The ACME Fuel Company is testing three gasoline additives that potentially improve miles per gallon (mpg): Data on the mpg increases are in the file gas.txt: (a) For each of the three additives, make boxplots, probability plots run Anderson-Darling tests, and Shapiro-Wilks tests to check for normality. (b) Based the results in part (a), which test (Hartley' s F-max; Bartlett's, Levene's) is best to use to check for a difference between the variances of mpg increases for the three additives? (c) Run the test you suggested in part (b): Be sure to state the null and alternative hypotheses, test statistic _ p-value, and conclusion_