Jane and Ashley take 20 days and 10 days respectively to complete a project when they work on it alone. They thought if they worked on the project together, they would take fewer days to complete it. During the period that they were working together, Jane took an eight day leave from work. This led to Jane's working for four extra days on her own to complete the project. How long did it take to finish the project ?  Choose the correct choice from the following answers.
A) 12 days
B) 15 days
C) 16 days
D) 18 days
E) 20 days

Rationale: "let us assume that the work is laying 40 bricks . jane = 2 bricks per day ashley = 4 brick per day together = 6 bricks per day let ' s say first 8 days ashley works alone , no of bricks = 32 last 4 days jane works alone , no . of bricks = 8 remaining bricks = 40 - 40 = 0 so together , they would take 0 / 6 = 0 total no . of days = 8 + 4 + 0 = 12 answer is a"
Answer: A