9.7. In order to ensure efficient usage of a server, it is necessary to estimate the mean number of concurrent users. According to records, the average number of concurrent users at 100 randomly selected times is 37.7, with a standard deviation σ=9.2. (a) Construct a 90% confidence interval for the expectation of the number of concurrent users. (b) At the 1% significance level, do these data provide significant evidence that the mean number of concurrent users is greater than 35 ?