A car-rental company is interested in the amount of time its vehicles are out of operation for repair work. state all assumptions and find a 90% confidence interval for the mean number of days in a year that all vehicles in the company's fleet are out of operation if a random sample of 10 cars showed the following number of days that each had been inoperative. 10 13 20 15 17 22 8 14 19 7 state all assumptions. select all the assumptions below. a. the sample comes from a normal population b. the sample size is at least 30 c. it is a random sample d. the variance is less than the mean find a 90% confidence interval for the population mean. the 90% confidence interval is from a lower limit of nothing to an upper limit of nothing. (round to two decimal places as needed.)