A large pile of rocks sitting in the sunshine in my backyard contains about 600 rocks, and the average temperature of each rock is 75 degrees, with a standard deviation of 4 degrees. I am going to take a random sample of 40 rocks from this pile. Find the probability that the average temperature of the 40 rocks will be less than 73 degrees. As part of your calculation you should do four things: describe how you know the sampling distribution is approximately normal, verify that the observations are (close to) independent, show your work, and find the probability.