Pleases solve both parts

A random sample of 36 mid-sized cars tested for fuel consumption gave a mean of 26.4 miles per gallon with a standard deviation of 2.3 miles per gallon. (a) Construct a 99% confidence interval for the population mean, u, and state the assumption(s) required. (b) Suppose the confidence interval obtained in part (a) is too wide. How can the width of this interval be reduced? Describe all possible alternatives. Which alternative is the best and why