About. com’s list of 20 World Class Orchestras includes the following from the United States: Boston Symphony Orchestra, Chicago Symphony Orchestra, Cleveland Orchestra, Los Angeles Philharmonic, New York Philharmonic, the Metropolitan Opera Orchestra, and the San Francisco Symphony. Choose 5 at random from the list of 20 for a benefit CD. What is the probability that the collection will include at least one group from the United States? At least 2 from the United States? That all 5 will be from the United States?