To estimate the average daily consumption (in milligrams) of nutritional supplements taken by professional baseball players, a sample of players is randomly selected from the population of major league and minor league players. For the sample, average daily consumption is reported to be 1940 mg., with a sample standard deviation of 260 mg. Show the 90% confidence interval estimate of the average daily amount of supplements consumed by the population of players if sample size is
a. 20
b. 41
c. 121