a survey is being planned to determine the average amount of time junior highschool students spend on social media including tiktok. a pilot survey indicated that the meantime per week is 12 hours with a population standard deviation of 3 hours. it is desired toestimate the mean viewing time within one-quarter of an hour with 90% confidence. how manystudents should be included in the survey to get this 90% confidence interval with a width of2*(1/4)