It is known that the standard deviation in the volumes of 20-ounce (591-millliliter) bottles of natural spring water bottled by a particular company is 5 millliliters. One hundred bottles are randomly sampled and measured.

• a. Calculate the standard error of the mean.
• b. Find the margin of error of a 90% confidence interval estimate for the population mean volume.
• c. Calculate the width for a 98% confidence interval for the population mean volume.