3 machines have a productivity ratio of 1 to 2 to 5. All 3 machines are working on a job for 3 hours. At the beginning of the 4th hour, the slowest machine breaks. It is fixed at the beginning of hour-seven and begins working again. The job is done in nine hours. What was the ratio of the work performed by the fastest machine as compared to the slowest?

A. 5
B 7
C 15/2
D 17/2
E 12

[spoiler]OA=C[/spoiler]

Source: Manhattan GMAT