IQ scores are normally distributed with a mean of 100 and a standard deviation of 15. Membership in Mensa requires an IQ score above 131.5. (a) If one person is randomly selected from the general population, find the probability of getting someone with an IQ score of at least 131.5. (b) If a random sample of 3 people is selected from the general population, find the probability of them having a mean IQ of at least 131.5.