The lengths of lumber a machine cuts are normally distributed with a mean of 90 inches and a standard deviation of 0.5 inch. (a) What is the probability that a randomly selected board cut by the machine has a length greater than 90.21 inches? (b) A sample of 41 boards is randomly selected. What is the probability that their mean length is greater than 90.21 inches? (a) The probability is | (Round to four decimal places as needed.) (b) The probability is (Round to four decimal places as needed.)