In anticipation of losses from projects running during the pandemic, the company audits cost…

In anticipation of losses from projects running during the pandemic, the company audits cost overrun of 20 projects with an average time of 3 months (90 days). Based on information from the audit team project, there is a deviation (standard deviation) in the audit, which is 10 days.
a) At the 95% confidence level, can the company complete the project audit the fastest in less than 88 days? Explain by calculating the lower limit confidence interval
(Lower Limits)!
b) If there are only 90 days left until the end of the year, can the company achieve this target? with the various uncertainties faced in convincing the new customer Explain by calculating the upper limit confidence interval (Upper Limit)!
c) If the confidence level is increased to 99%, calculate the lower limit confidence interval and the upper limit of the population mean number of days to acquire these additional customers? Explain the difference?