If A, B and C together can finish a piece of work in 4 days. A alone in 12 days and B in 18 days, then C alone can do it in?
Options.
A) 7 days	B) 3 days	C) 9 days	D) 8 days	E) 2 days

Rationale: "c 9 days c = 1 / 4 - 1 / 12 – 1 / 18 = 1 / 9 = > 9 days"
Answer: C