Three students shared a group project, jack claimed that he do the project by himself in 20 hours, and Jane in 30 hours. Jack started working on the project for 10 hours, then Jane continued working on it another 10 hours. Lastly, Julie joined the team and working 10 hours, the project was completed. How many hours it takes Julie to finish the project by herself?	Choose the correct option: A) 70 hours B) 60 hours C) 50 hours D) 40 hours E) 30 hours
10/20 + 10/30 + 10/x = 1
x = 60 hours
ANSWER:60 hours
<result>B</result>
Three students shared a group project, jack claimed that he do the project by himself in 20 hours, and Jane in 30 hours. Jack started working on the project for 10 hours, then Jane continued working on it another 10 hours. Lastly, Julie joined the team and working 10 hours, the project was completed. How many hours it takes Julie to finish the project by herself?