In a study, the mean number of days that 111 adolescents in substance abuse treatment used medical marijuana in the last 6 months was 111.68. Assuming the population standard deviation is 31 days, a 99% confidence interval for the mean number of days, u, of medical marijuana use in the last 6 months of all adolescents in substance abuse treatment is from 104.10 to 119.26, and a 90% confidence interval for the mean is from 106.84 to 116.52. Complete parts (a) through (c) below. Click here to view page 1 of the table of areas under the standard normal curve. Click here to view page 2 of the table of areas under the standard normal curve. . . . a. Determine the margin of error for the 99% confidence interval. day(s) (Round to two decimal places as needed.) b. Determine the margin of error for the 90% confidence interval. day(s) (Round to two decimal places as needed.)