Bloomberg L.P. lists the top 20 U.S. companies by revenue. Walmart stores is number one followed by Exxon Mobil and Chevron. Of the 20 companies on the list, 8 are in some type of electronics- related business. Suppose four firms are randomly selected. a. What is the probability that none of the firms is in some type of electronics-related business? b. What is the probability that all four of the firms is in some type of electronics-related business? c. What is the probability that exactly two of the firms is in some type of electronics-related business?