A is twice as good a workman as B and they took 6 days together to do the work B alone can do it in?  Select the correct option:
A) 25 days	B) 18 days	C) 21 days	D) 11 days	E) 13 days

Rationale: "wc = 2 : 1 2 x + x = 1 / 6 x = 1 / 18 = > 18 days answer : b"
Answer: B