WUCSUVIR The monthly incomes for 12 randomly selected people, each with a bachelor's degree in economics, 4450.74 4596.24 4366.06 are shown on the right. Complete parts (a) through (c) below. 4455.45 4151.86 3727.02 Assume the population is normally distributed. 4283.05 4527.46 4407.19 3946.34 4023.52 4221.96 (a) Find the sample mean. X = (Round to one decimal place as needed.) (b) Find the sample standard deviation. s = 260.1 (Round to one decimal place as needed.) (c) Construct a 99% confidence interval for the population mean u. A 99% confidence interval for the population mean is ( 4029.7 , 4496.1 ). (Round to one decimal place as needed.)