7". The operations division manager of a logistics company is trying to identify whether the use of nitrogen to fill tires instead of normal air improves fuel economy. The tires of 12 trucks were filled with nitrogen and tested over a prescribed course. Without changing drivers, the tires of the same trucks were then filled with normal air and driven once again over the test course. The mileage was recorded as follows: Mileage {in kilometersf'liter] Using Nitrogen Using Normal Air H D 3 4 5 6 T 8 9 H H a. Test whether using nitrogen instead of normal air improves fuel economy [increases the mileage] at 0.05 level of significance. b. Find a 95% confidence interval of the difference between the mean of mileage of trucks whose tires is filled with nitrogen and the mileage of trucks filled whose tires is filled with normal air