Please reason step by step, and put your final answer within \boxed{}.
Bill downloads the movie Revenge of the Avengers to his computer using a download manager that downloads from 3 sources marked A, B, and C. Each source provides download at a constant rate, but the rates of different sources are not necessarily identical. If the movie was downloaded from sources A and C alone, it would take 4 hours to complete the download. The next day, source B is available, but the other sources are inactive. It takes 40 hours to download the trailer of the movie, a file that is 10 times smaller, from source B alone. How long did it take to download the movie using all three sources?
user