4 [Total 7 Marks] Automotive researchers have reported that building a 1.6 Liter car requires an average of 22.3 labor hours. To confirm this claim, Toyota Altis choose a random sample of 324 cars and found the mean 24.5 labor hours, with a sample standard deviation of 6 labor hours. (a) Calculate the standard error of the mean. [1 Mark] (b) Calculate a 99% confidence interval for the true mean labor hours for building 1.6 Liter cars. Give the upper and lower limits of this interval to one decimal place. [4 Marks] (c) Does the sample support the claim made by automotive researchers? Explain with reference to the interval that you have calculated in part (b)