It is known that driving can be difficult in regions where winter conditions involve snow-covered roads. for cars equipped with all-season tires traveling at 90 kilometers per hour, the mean stopping time in fresh snow is known to be 215 meters, with a standard deviation of σ = 2.5 meters. it is often advocated that automobiles in such areas should be equipped with special tires to compensate for such conditions, especially with respect to stopping distance. a manufacturer of tires made for driving in fresh snow claims that vehicles equipped with their tires have a decreased stopping distance. a study was done using a random sample of nine snow tires from the manufacturer on a snow-covered test track. the tests resulted in a mean stopping distance of = 212.9 meters. using the sample results and assuming that stopping distance is a normally distributed random variable, what is the value of the test statistic?