The age difference between Lucy and Bill is $$20~-- 12 = 8$$, which will not change. Thus, Lucy is $$17 + 8 = 25$$ years old. 
Lucy was $$20$$ years old when Bill was $$12$$. Now, Bill is $$17$$ years old. How old is Lucy? 

[A] $$12$$ 
[B] $$13$$ 
[C] $$21$$ 
[D] $$23$$ 
[E] $$25$$ 