The table below shows the weekly change in the price of one gram of gold for four weeks. By how much did the price of one gram of gold change from the beginning of week 1 to the end of week 4?

Suppose a batch of steel rods produced at a steel plant have a mean length of 150 millimeters, and a standard deviation of 12. if 100 rods are sampled at random from the batch, what is the probability that the mean length of the sample rods would differ from the population mean by less than 0.5 millimeters?