Subject: mathqa
Question: abel can complete a work in 10 days , ben in 12 days and carla in 16 days . all of them began the work together , but abel had to leave after 2 days and ben 4 days before the completion of the work . how long did the work last ?
Option: 
A: 7
B: 10
C: 9
D: 7 2 / 3
Answer: D