An advertising executive wants to estimate the mean amount of time that consumers spend with digital media daily. From past studies, the standard deviation is estimated as 39 minutes. a. What sample size is needed if the executive wants to be 90% condent of being correct to within 14 minutes? b. If 95% confidence is desired, how many consumers need to be selected? a. A sample size of D consumers is needed. (Round up to the nearest integer.) b. If 95% condence is desired, consumers need to be selected. (Round up to the nearest integer.)