X can finish a work in 30 days, Y can finish a work in 12 days and Z can finish a work in 15 days. Y and Z start the work, but are forced to leave after 3 days. The remaining work was done by X in how many days?

A

9 days

B

16 $$\frac{1}{2}$$ days

C

8 $$\frac{1}{2}$$ days

D

18 $$\frac{1}{2}$$ days