Acar dealer who sells only late-model luxury cars recently hired a new salesperson and believes that this salesperson is selling at lower markups. he knows that the long-run average markup in his lot is $5,600. he takes a random sample of 16 of the new salesperson's sales and finds an average markup of $5,000 and a standard deviation of $800. assume the markups are normally distributed. what is the value of an appropriate test statistic for the car dealer to use to test his claim?