The law firm of Dewey, Cheetham, and Howe files claims against unscrupulous car repair shops that take advantage of consumers who know nothing about cars. A lawyer who takes a 20-minute break after every two hours of work can process one claim with six hours of work. If the lawyer takes a 20-minute break after every four hours of work she can process one claim with eight hours of work. If she takes a 20-minute break after every hour of work she can process one claim with just five hours of work. Which of these is the efficient method of production for Dewey, Cheetham, and Howe?