21. A random sample of 50 CSCC students has a mean GPA of 2.55. It is known that the population standard deviation for the GPA of all CSCC students is 1.1. Use this information to complete the following: a) Does the information above provide an estimate of a population mean or a population proportion? b) Provide a point estimate for the population mean GPA of all CSCC students. c) Construct and interpret a 95% confidence interval for the parameter you selected in part (a). d) What is the margin of error of this interval estimate? e) How large of a sample would you need if you wanted your 95% confidence interval to be within 0.2 units of the population parameter