Kerry rented a limousine for prom. There was a one-time charge of $200. You will then pay an hourly rate of $50. Her total cost for the night was $800. How many hours did Kerry rent the limo for?

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?