On a recent Saturday, a total of 1440 people visited a local library. Of these people, 248 were under age 10, 471 were aged -, 10-18, 169 were aged -, and the rest were more than 30 years old. One person is sampled at random. (a) What is the probability that the person is less than 19years old? (b) What is the probability that the person is more than 18 years old?.