Albert can do a piece of work in 9 hours . Brian can do the same work in 12…

Albert can do a piece of work in 9 hours . Brian can do the same work in 12 hours and Charles in 15 hours . Albert , Brian and Charles start the same work at 9am , while Albert stops at 11 am and Brian stops at 12 noon . Charles work till the end of work . At what time will the work completes ?