the rocky mountain district sales manager of rath publishing incorporated, a college textbook publishing company, claims that the sales representatives make an average of 39 sales calls per week on professors. several reps say that this estimate is too low. to investigate, a random sample of 25 sales representatives reveals that the mean number of calls made last week was 40. the standard deviation of the sample is 3.8 calls. using the 0.100 significance level, can we conclude that the mean number of calls per salesperson per week is more than 39?