A can do a certain work in 15 days. B is 10% less efficient than A, and C is 10% more efficient than A. All the three work together for 3 days. The remaining work is completed by D alone in $$9\frac{1}{2}$$ days. D alone can complete the original work in:

A

18 days

B

15 days

C

25 days

D

20 days