The manager of a fleet of automobiles is testing two brands of radial tires and assigns one tire of each brand at random to the two rear wheels of eight cars and runs the cars until the tires wear out. The data (in kilometers) follow. Find a 99% confidence interval on the difference in mean life which brand would you prefer, based on this calculation?

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Brand 1 Brand 2 Car 36,925 34,318 45,300 42,280 36,240 35,500 32,100 31,950 37,210 38,015 48,360 47,800 38,200 37,810 8. 33,500 33,215