a. The average lifespan of a certain brand of washing machine is 6 years, with a standard deviation of 0.5 years. Assume that the lifespan of this brand of washing machine is normally distributed. i. What is the probability that a randomly selected washing machine of this brand will last for 5.2 years or less? [2] ii. If you select a random sample of 15 washing machines, what is the probability that the sample mean lifespan is between 5.8 years and 6.3 years?