6. The mean annual cost of automobile insurance is $939 (CNBC, February 23, 2006) Assume that the standard deviation is $245. What is the probability that a sample of automobile insurance policies will have a sample mean within $25 of the population mean for each of the following sample a. sizes: 30, 50, 100, and 400? b. What is the advantage of a larger sample size when attempting to estimate the popu- lation mean