A 2010 study conducted by the National Center for Health Statistics found that 25% of U.S. households had no landline service. This raises concerns about the accuracy of certain surveys, as they depend on random-digit dialing to households via landlines. We are going to pick five U.S. households at random:
a) What is the probability that all five of them have a landline?
b) What is the probability that at least one of them does not have a landline?
c) What is the probability that at least one of them does have a landline?