Time&Work Data Sufficiency

A and B together can complete a task in 7 days. B alone can do it in 20 days. What part of the work was carried out by A?

I. A completed the job alone after A and B worked together for 5 days.
II. Part of the work done by A could have been done by B and C together in 6 days.

A.  I alone sufficient while II alone not sufficient to answer
B.  II alone sufficient while I alone not sufficient to answer
C.  Either I or II alone sufficient to answer
D.  Both I and II are not sufficient to answer
E.  Both I and II are necessary to answer.

Watch this space for answer in a week.