20. A random variable is normally distributed with mean, u = $1500 and standard deviation, o = $50. What is the standard error of the sampling distribution of the mean for a sample of size 100? 21. A random variable that is normally distributed with u = 210 and o = 20. What is the probability that a simple random sample of 4 items will have a mean less than 225? 22. If x is normally distributed with u = 40.0 and o = 4.0, determine the following probabilities. P (x = 40.0 )