From past experience, a stockbroker believes that under the present economic conditions, a customer will invest in tax-free bonds with a probability of 0.6 , will invest in mutual funds with a probability of 0.3 , and will invest in both tax-free bonds and mutual funds with a probability of 0.2 . At this time, find the probability that a customer will invest
(a) in either tax-free bonds or mutual funds;
(b) in neither tax-free bonds nor mutual funds.