If A, B and C together can finish a piece of work in 4 days. A alone in 36 days and B in 18 days, then C alone can do it in?
Pick one:  A) 1  B) 7  C) 8  D) 9  E) 6

Rationale: "c = 1 / 4 - 1 / 36 – 1 / 18 = 1 / 6 = > 6 days ' answer : e"
Answer: E