You would like to construct a 95% confidence interval to estimate the population mean time it takes drivers to react following the application of brakes by the driver in front of them. You take a random sample of reaction time measurements and compute their mean to be 2.5 seconds and their standard deviation to be 0.4 seconds. (a) What is the best point estimate, based on the sample, to use for the population mean? (b) For each of the following sampling scenarios, determine which distribution should be used to calculate the critical value for the 95% confidence interval for the population mean.