Dan can do a job alone in 12 hours. Annie, working alone, can do the same job in just 9 hours. If Dan works alone for 8 hours and then stops, how many hours will it take Annie, working alone, to complete the job? Choose the most appropriate option
A) 2	B) 3	C) 4	D) 5	E) 6
Dan can complete 1/12 of the job per hour.   In 8 hours, Dan completes 8(1/12) = 2/3 of the job.   Annie can complete 1/9 of the job per hour.   To complete the job, Annie will take 1/3 / 1/9 = 3 hours.   The answer is 3.
<result>B</result>
Dan can do a job alone in 12 hours. Annie, working alone, can do the same job in just 9 hours. If Dan works alone for 8 hours and then stops, how many hours will it take Annie, working alone, to complete the job?