This please :)

4. A random sample of 16 brand A cigarettes have nicotine contents with x = 16.3 and s = 2.4mg. Assume the amount of nicotine per cigarette has a near normal distribution. (a) Compute a 99% confidence interval for this mean. (b) Approximately, how large of a sample is needed so i and u do not differ by more than 1mg with 99% confidence? Numerical answer please. (c) Comparing with (b), do you expect more or less sample size needed so a and u do not differ by more than 1mg with 90% confidence? Explain your answer. Do not use numerical calculation