9.43 A taxi company is trying to decide whether to purchase brand A or brand B tires for its fleet of taxis. To estimate the difference in the two brands, an exper- iment is conducted using 12 of each brand. The tires are run until they wear out. The results are Brand A: = 36, 300 kilometers, 1=36,300 8 = 5000 kilometers. Brand B: 238, 100 kilometers, 82 6100 kilometers. Compute a 95% confidence interval for AB as- suming the populations to be approximately normally distributed. You may not assume that the variances are equal.