A company produces steel rods. The lengths of the steel rods are normally distributed with a mean of 158.3-cm and a standard deviation of 1-cm. For shipment, 21 steel rods are bundled together. Find the probability that the average length of a randomly selected bundle of steel rods is between 158.3-cm and 158.5-cm. P(158.3-cm < x < 158.5-cm) = Enter your answer as a number accurate to 4 decimal places.