two sister decided to watch all the episodes of a popular tv show on DVD. Abby has already watched 9 episodes and will continue to watch the show at a rate of 1 episoder per day. Erica, who hasn't yet seen the show, will start watching 2 episodes per day. once the two sister get to the points where they have watched the same number of episodes per day. Once the two sister get to the point where they have watched the same number of episodes, they plan to finish the series together. how many episodes will each sister have watched at that points? how long will that take?