You may need to use the appropriate appendix table or technology to answer this question. A population has a mean of 800 and a standard deviation of 200. Suppose a sample of size 400 is selected and x is used to estimate ????. (Round your answers to four decimal places.) (a) What is the probability that the sample mean will be within 5 of the population mean? (b) What is the probability that the sample mean will be within 10 of the population mean